LIBRARY 

UNIVERSITY  OF 
CALIFORNIA 
SAN  DIEGO 


ANIMAL  LIFE  AND  INTELLIGENCE. 


j^  LLOYD    .MORGAN,   F.G.S., 

PROFESSOR   IN   AND   DEAN   OF   UNIVERSITY   COLLEGE,    BRISTOL; 
LECTURER   AT  THE    BRISTOL   MEDICAL   SCHOOL; 

PRESIDENT  OF  THE  BRISTOL  NATURALISTS'  SOCIETY,  ETC. 

AUTHOR  OF 
"ANIMAL  BIOLOGY,"  "THE  SPRINGS  OF  CONDUCT,"  ETC. 


BOSTON,  U.S.A.: 

GIXX   &   COMPANY,   PUBLISHERS. 
1891. 


TO 

MY  FATHER. 


PREFACE. 


THERE  are  many  books  in  our  language  which  deal  with 
Animal  Intelligence  in  an  anecdotal  and  conventionally 
popular  manner.  There  are  a  few,  notably  those  by  Mr. 
Eomanes  and  Mr.  Mivart,  which  bring  adequate  knowledge 
and  training  to  bear  on  a  subject  of  unusual  difficulty.  In 
the  following  pages  I  have  endeavoured  to  contribute  some- 
thing (imperfect,  as  I  know  full  well,  but  the  result  of 
several  years'  study  and  thought)  to  our  deeper  knowledge 
of  those  mental  processes  which  we  may  fairly  infer  from 
the  activities  of  dumb  animals. 

The  consideration  of  Animal  Intelligence,  from  the 
scientific  and  philosophical  standpoint,  has  been  my 
primary  aim.  But  so  inextricably  intertwined  is  the 
subject  of  Intelligence  with  the  subject  of  Life,  the  subject 
of  organic  evolution  with  the  subject  of  mental  evolution, 
so  closely  are  questions  of  Heredity  and  Natural  Selection 
interwoven  with  questions  of  Habit  and  Instinct,  that  I  have 
devoted  the  first  part  of  this  volume  to  a  consideration 
of  Organic  Evolution.  The  great  importance  and  value 
of  Professor  Weismann's  recent  contributions  to  biological 
science,  and  their  direct  bearing  on  questions  of  Instinct, 
rendered  such  treatment  of  my  subject,  not  only  advisable, 
but  necessary.  Moreover,  it  seemed  to  me,  and  to  those 
whom  I  consulted  in  the  matter,  that  a  general  work  on 
Animal  Life  and  Intelligence,  if  adequately  knit  into  a 
connected  whole,  and  based  on  sound  principles  of  science 


vi  Preface. 

and  of  philosophy,  would  not  be  unwelcomed  by  biological 
students,  and  by  that  large  and  increasing  class  of  readers 
who,  though  not  professed  students,  follow  with  eager 
interest  the  development  of  the  doctrine  of  Evolution. 

Incidentally,  but  only  incidentally,  matters  concerning 
man,  as  compared  with  the  dumb  animals,  have  been 
introduced.  It  is  contended  that  in  man  alone,  and  in  no 
dumb  animal,  is  the  rational  faculty,  as  defined  in  these 
pages,  developed  ;  and  it  is  contended  that  among  human- 
folk  that  process  of  natural  selection,  which  is  so  potent  a 
factor  in  the  lower  reaches  of  organic  life,  sinks  into  com- 
parative insignificance.  Man  is  a  creature  of  ideas  and 
ideals.  For  him  the  moral  factor  becomes  one  of  the  very 
highest  importance.  He  conceives  an  ideal  self  which  he 
strives  to  realize  ;  he  conceives  an  ideal  humanity  towards 
which  he  would  raise  his  fellow-man.  He  becomes  a 
conscious  participator  in  the  evolution  of  man,  in  the 
progress  of  humanity. 

But  while  we  must  not  be  blind  to  the  effects  of  new 
and  higher  factors  of  progress  thus  introduced  as  we  rise 
in  the  scale  of  phenomena,  we  must  at  the  same  time 
remember  that  biological  laws  still  hold  true,  though  moral 
considerations  and  the  law  of  duty  may  profoundly  modify 
them.  The  eagle  soars  aloft  apparently  in  defiance  of 
gravitation ;  but  the  law  of  gravitation  still  holds  good ; 
and  no  treatment  of  the  mechanism  of  flight  which  neglected 
it  would  be  satisfactory.  Moral  restraint,  a  higher  standard 
of  comfort,  and  a  perception  of  the  folly  and  misery  of  early 
and  improvident  marriage  may  tend  to  check  the  rate  of 
growth  of  population  :  but  the  "  law  of  increase  "  still  holds 
good,  as  a  law  of  the  factors  of  phenomena  ;  and  Malthus 
did  good  service  to  the  cause  of  science  when  he  insisted 
on  its  importance.  We  may  guide  or  lighten  the  incidence 
of  natural  selection  through  competition ;  we  may  in  our 
pity  provide  an  asylum  for  the  unfortunates  who  are  suffer- 


Preface.  vii 

ing  elimination  ;  but  we  cannot  alter  a  law  which,  as  that 
of  one  of  the  factors  of  organic  phenomena,  still  obtains, 
notwithstanding  the  introduction  of  other  factors. 

However  profoundly  the  laws  of  phenomena  may  be 
modified  by  such  introduction  of  new  and  higher  factors, 
the  older  and  lower  factors  are  still  at  work  beneath  the 
surface.  And  he  who  would  adequately  grasp  the  social 
problems  of  our  time  should  bring  to  them  a  mind  prepared 
by  a  study  of  the  laws  of  organic  life :  for  human  beings, 
rational  and  moral  though  they  may  be,  are  still  organisms  ; 
and  man  can  in  no  wise  alter  or  annul  those  deep-lying 
facts  which  nature  has  throughout  the  ages  been  weaving 
into  the  tissue  of  life. 

Some  parts  of  this  work  are  necessarily  more  technical, 
and  therefore  more  abstruse,  than  others.  This  is  especially 
the  case  with  Chapters  III.,  V.,  and  VI. ;  while,  for  those 
unacquainted  with  philosophical  thought,  perhaps  the  last 
chapter  may  present  difficulties  of  a  different  order.  With 
these  exceptions,  the  book  will  not  be  beyond  the  ready 
comprehension  of  the  general  reader  of  average  intelligence. 

I  have  to  thank  many  kind  friends  for  incidental  help. 
Thanks  are  also  due  to  Professor  Flower,  who  courteously 
gave  permission  that  some  of  the  exhibits  in  our  great 
national  collection  in  Cromwell  Eoad  might  be  photographed 
and  reproduced ;  and  to  Messrs.  Longmans  for  the  use  of 
two  or  three  illustrations  from  my  text-book  of  "Animal 
Biology." 

C.  LLOYD  MOEGAN. 

UNIVERSITY   COLLEGE,  BRISTOL, 
October,  1890. 


CONTENTS. 


CHAPTER  I. 

THE   NATURE    OF   ANIMAL   LIFE. 

PAGE 

The  characteristics  of  animals       ..  ..  ..  ..  ••         2 

The  relation  of  animals  to  food-stuffs  . . 

„  „  „         the  atmosphere  , .  . .  . .  . .       15 

„  „  „         energy 

CHAPTER  II. 

THE   PROCESS  OF  LIFE. 

Illustration  from  respiration          . .             . .             . .  . .                      21 

„     nutrition      ..             ..             ..  ..                              25 

The  utilization  of  the  materials  incorporated 

The  analogy  of  a  gas-engine.     Explosive  metabolism  . .                            30 

CHAPTER  III. 

REPRODUCTION  AND  DEVELOPMENT. 

Keproduction  in  the  protozoa  ..             ..             ..             ..             ..37 

Fission  in  the  metazoa            . .  . .             . .             . .             . .              41 

The  regeneration  of  lost  parts  . .             . .             . .             . .                      41 

Keproduction  by  budding       . .  . .             . .             . .             . .              42 

Sexual  reproduction        . .  . .               .             .               . .                      42 

Illustration  of  development    . .  . .             . .             . .             . .              51 

Parental  sacrifice             . .  . .             . .             . .             . .                      56 

The  law  of  increase . .  58 


CHAPTER  IV. 

VARIATION   AND   NATURAL   SELECTION. 

The  law  of  persistence    . .             . .             . .             . .  . .                      61 

The  occurrence  of  variations  . .             . .             . .             . .  .  .              63 

Application  of  the  law  of  increase                . .               .  . .                      76 

Natural  selection     ,  77 


Contents. 


Elimination  and  selection  . .  . .       79 

Modes  of  natural  elimination  illustrated 

Protective  resemblance  and  mimicry  . .  . .       82 

Selection  proper  illustrated   .. 

The  effects  of  natural  selection     .. 

Isolation  or  segregation 

Its  modes,  geographical,  preferential  and  physiological  . .  .  •       99 

Its  effects   ..  ..  ..  ..  ..  ..  ..  108 

Utility  of  specific  characters 

Variations  in  the  intensity  of  the  struggle  for  existence  . . 

Convergence  of  characters  . .  . .  . .  . .  . .     117 

Modes  of  adaptation :  Progress 

Evolution  and  Revolution  •  •     120 


CHAPTER  V. 

HEREDITY   AND    THE   ORIGIN   OF   VARIATIONS. 

Heredity  in  the  protozoa               . .             . .  . .             . .             . .     123 

Regeneration  of  lost  parts      . .             . .             . .  . .                            124 

Sexual  reproduction  and  heredity                . .  . .             . .             . .     129 

The  problem  of  hen  and  egg  . .             . .             . .  . .             . .             130 

Reproductive  continuity                .  .             . .  . .                            . .     131 

Pangenesis               . .             . .             . .             . .  . .             . .             131 

Modified  pangenesis        . .             . .             . .  . .             . .             . .     134 

Continuity  of  germ-plasm       . .             . .             . .  . .             . .             138 

Cellular  continuity  with  differentiation       . .  . .             . .             . .     142 

The  inheritance  or  non-inheritance  of  acquired  characters  . .             146 

Origin  of  variations  on  the  latter  view        . .  . .             . .             . .     149 

Hypothesis  of  organic  combination      . .             . .  . .             . .             150 

The  extrusion  of  the  second  polar  cell         ..  ..             ..             ..153 

The  protozoan  origin  of  variations  -     . .             . .  . .             . .             156 

How  can  the  body  influence  the  germ  ?  . .             . .             . .     159 

Is  there  sufficient  evidence  that  it  does  ?             . .  . .             . .             162 

Summary  and  conclusion               . .             . .  . .             . .             . .     175 

CHAPTER   VI. 

ORGANIC    EVOLUTION. 

The  diversity  of  animal  life           . .             . .  . .             . .             . .     177 

The  evolution  theory              . .             . .             . .  . .             . .             181 

Natural  selection  :  not  to  be  used  as  a  magic  formula  . .             . .     183 

Panmixia  and  disuse              . .             . .             . .  . .             . .             189 

Sexual  selection  or  preferential  mating       . .  . .             . .             . .     197 

Use  and  disuse         . .             . .             . .             . .  . .             . .            209 

The  nature  of  variations. .             . .             . .  . .             . .             . .     216 

The  inheritance  of  variations                . .             . .  . .             . .            223 

The  origin  of  variations  . .             . .             . .  . .             . ,             . .     231 

Summary  and  conclusion        . .             . .             . .  . .             . .            241 


Contents. 


CHAPTER  VII. 

THE    SENSES   OF   ANIMALS. 

PAGE 

Tbe  primary  object  of  sensation    . .  . .     243 

Organic  sensations  and  tbe  muscular  sense         . .  244 

Touch                . .             . .             . .             . .  . .             . .     245 

The  temperature-sense           . .             . .               .  . .             249 

Taste..             ..             ..             ..             ..  ..              ..             ..250 

Smell          ..             ..             ..             ..             .-.  ,          ..             ..            257 

Hearing            ..             ..             ..             ..  ..             ..             ..261 

Sense  of  rotation  or  acceleration           . .             . .  •         . .             . .            269 

Sight  . .             . .             . .             . .             . .  ..."             . .     273 

Restatement  of  theory  of  colour-vision                . .  . .             . .             278 

Variation  in  the  limits  of  colour-vision       . .  . .             . .             . .     281 

The  four  types  of  "  visual "  organs       . .             . .  . .             . .             293 

Problematical  senses      . .             . .             . .  . .             . .             . .     294 

Permanent  possibilities  of  sensation     . .             . .  . .             . .             298 


CHAPTER  VIII. 

MENTAL    PEOCESSES    IN   MAN. 

The  physiological  aspect                . .  . .  . .             . .             . .     302 

The  psychological  aspect        . .             . .             . .  . .  . .            304 

Sensations :  their  localization,  etc.  . .  . .             . .             . .     306 

Perceptual  construction         . .                            . .  . .  312 

Conceptual  analysis         . .             . .  . .  . .             .  .             . .     321 

Inferences  perceptual  and  conceptual  . .             . .  . .  . .            328 

Intelligence  and  reason  . .             . .  . .  . .             . .             . .     330 


CHAPTER  IX. 

MENTAL    PROCESSES   IN   ANIMALS  :    THEIR   POWERS   OF   PERCEPTION   AND 
INTELLIGENCE. 

The  two  factors  in  phenomena       . .             . .  . .             . .             . .     331 

The  basis  in  organic  evolution              . .             . .  . .             . .             336 

Perceptual  construction  in  mammalia         . .  . .             . .             . .     338 

Can  animals  analyze  their  constructs  ?                . .  . .             . .            347 

The  generic  difference  between  the  minds  of  man  and  brute  . .  . .     350 

Perceptual  construction  in  other  vertebrates       . .  . .             . .            350 

"  Understanding  "  of  words           . .             . .  . .             . .             .  .     354 

Perceptual  construction  in  the  invertebrates       . .  . .             . .            356 

"  The  psychic  life  of  micro-organisms  "  . .             . .             . .     360 

The  inferences  of  animals       . .             . .             . .  . .             . .            361 

Intelligent  not  rational   . .             . .             . .  . .             . .             .  .     365 

Use  of  words  defined               . .             . .             . .  . .             . .             372 

Language  and  analysis   ..             ..             ..  ..             ..             .,     374 


Contents. 


CHAPTER  X. 

THE   FEELINGS    OF   ANIMALS:    THEIR   APPETENCES   AND    EMOTIONS. 

PAGE 

Pleasure  and  pain  :  their  organic  limits      . .  . .             . .     379 

Their  directive  value              ..             ..             ..  ..             ...            380 

An  emotion  exemplified  . .             . .             . .  . .             . .             . .     382 

Sensitiveness  and  sensibility-..             ..             ..  ..             ..            385 

The  expression  of  the  emotions     . .             . .  . .             . .             . .     385 

The  postponement  of  action  . .             . .             . .  . .             . .             385 

The  three  orders  of  emotion          . .             . .  . .             . .             . .     390 

The  capacities  of  animals  for  pleasure  and  pain  . .             . .            391 

Sense-feelings  . .             . .             . .             . .  . .             . .             . .     393 

Some  emotions  of  animals      . .             . .             . .  . .             . .             395 

The  necessity  for  caution  in  interpretation  . .  . .             . .             . .     399 

The  sense  of  beauty                . .             . .             . .  . .             . .            407 

Can  animals  be  moral  ?  . .             . .             . .  . .             . .             . .     413 

Conclusion                . .             . .             . .             . .  . .             . .            414 

CHAPTER  XI. 

ANIMAL   ACTIVITIES  :    HABIT   AND  INSTINCT. 

The  nature  of  animal  activities     ..             ..  ..             ..             ..415 

The  outer  and  inner  aspect    .  .             . .             . .  . .             . .            417 

The  inherited  organization            . .  . .             . .             . .     419 

Habitual  activities  . .             . .             . .             . .  . .             . .             420 

Instinctive  activities       . .             . .             . .  . .             . .             . .     422 

Innate  capacity        . .             . .             . .             . .  . .             . .             426 

Blind  prevision                . .             . .             . .  . .             . .             . .     429 

Consciousness  and  instinct     . .             . .             . .  . .             . .            432 

Mr.  Komanes's  treatment  of  instinct            . .  . .             . .             . .     434 

Lapsed  intelligence  and  modern  views  on  heredity  . .             . .            435 

Three  factors  in  the  origin  of  instinctive  activities  . .             . .             . .     447 

The  emotional  basis  of  instinct             . .             . .  . .             . .            449 

The  influence  of  intelligence  on  instinct    . .  . .             . .             . .     452 

The  characteristics  of  intelligent  activities         . .  . .             . .            456 

The  place  of  volition       ..             ..             ..  ..                            ..459 

Perceptual  and  conceptual  volition      . .             . .  . .                            460 

Consciousness  and  consentience    . .             . .  . .             . .             . .     46 1 

Classification  of  activities       ..             ..             ..  ..             ..             462 

CHAPTER  XII. 

MENTAL     EVOLUTION. 

Is  mind  evolved  from  matter  ?       ..             ..  ..             ..             ..464 

Kinesis  and  metakinesis        . .             . .             . .  . .             . .            467 

Monistic  assumptions      . .             . .             . .  . .             . .             . .     470 

The  nature  of  ejects                . .                            . .  . .             . .             476 


Contents.  xiii 


PAGE 

The  universe  as  eject      . .             . .             . .  . .             . .             . .     478 

Metakinetic  environment  of  mind        . .             . .  . .             . .            481 

Conceptual  ideas  not  subject  to  natural  selection  . .             . .             . .     483 

Elimination  through  incongruity         . .              . .  . .              . .             486 

Intemeural  evolution      . .             . .             . .  . .             . .             .  .     490 

Interpretations  of  nature        . .             . .             . .  . .             ...          492 

Gun  fetishism  have  had  a  natural  genesis  ?  . .             . .             . .     493 

The  origin  of  interneural  variations     . .             . .  . .             . .            496 

Are  acquired  variations  inherited  ?              . .  . .             . .             . .     497 

Summary  and  conclusion       . .             . .             . .  . .             . .            501 


LIST   OF   ILLUSTRATIONS. 


FIG.  PAGB 

KENTISH  PLOVEK  WITH  EGGS  AND  YOUNG  Frontispiece 

1.  SPIRACLES  AND  AIH-TTJBES  OF  COCKROACH  ..            ..            ..        3 

2.  GILLS  OF  MUSSEL            . .             . .             . .  . .             . .                4 

3.  A  CELL  GREATLY  MAGNIFIED               . .  11 

4.  AM<EBA              . .             . .             . .             . .  . .             . .               12 

5.  EGG-CELL  AND  SPERM-CELL    . .            . .  . .                                    13 

6.  DIAGRAM  OF  CIRCULATION             ....  23 

7.  PROTOZOA   . .            . .            . .            . .  . .                     38 

8.  HYDRA  VIRIDES              . .             . .             . .  . .            . .              43 

9.  AURELIA  :  LIFE-CYCLE            . .             . .  . .             . .                      45 

10.  LITER-FLUKE— EMBRYONIC  STAGES             ;.  . .            . .             47 

11.  DIAGRAM  OF  DEVELOPMENT    ..            ..  ..            ..            ..51 

12.  WING  OF  BAT  (PIPISTRELLE)        ....  . .            . .              64 

13.  VARIATIONS  OF  THE  NOCTULE              ..'  ..            ..             ..67 

14.  „              „        LONG-EARED  BAT       . .  . .            . .              68 

15.  „              „        PIPISTRELLE        ..  ..             ..            ..69 

16.  „              „        WHISKERED  BAT        . .  . .            . .              70 

17.  VARIATIONS  ADJUSTED  TO  THE  STANDARD  OF  THE  NOCTULE        . .       73 

18.  CATERPILLAR  OF  A  MOTH  ON  AN  OAK  SPRAY          ..  ..              85 

19.  LOCUST  RESEMBLING  A  LEAF                .  .  .  .            .  .            .  .       86 

20.  MIMICRY  OF  BEES  BY  FLIES         . .             . .  . .             . .              91 

21.  EGG  AND  HEN         ..  ..             ..             ..     141 

22.  STAG-BEETLES    ..             ..            ..            ..  ..            ..            180 

23.  TACTILE  CORPUSCULES            . .             . .  . .            . .            . .     247 

24.  TOUCH-HAIR  OF  INSECT    . .            . .            . .  . .            . .            248 

25.  TASTE-BUDS  OF  RABBIT           . .             . .  . .            . .            . .     250 

26.  ANTENNULE  OF  CRAYFISH              . .            . .  . .            . .            259 

27.  DIAGRAM  OF  EAR    . .             . .             . .  . .            . .            . .     263 

28.  TAIL  OF  MYSIS                . .            . .            . .  . .             . .            266 

29.  LEG  OF  GRASSHOPPER             . .             . .  . .            . .            . .     266 

30.  DIAGRAM  OF  SEMICIRCULAR  CANALS  270 


xvi  List  of  Illustrations. 

FIG.  PAGE 

31.  THE  HUMAN  EYE    . .            . .            . .            . .  . .             . .     274 

32.  EETINA  OF  THE  EYE      . .            . .             . .  . .             . .            274 

33.  VARIATION  IN  THE  LIMITS  OF  COLOUR- VISION  . .  . .             . .     281 

34.  PINEAL  EYE      . .             . .             . .             . .  . .             . .            288 

35.  SKULL  OF  MELANERPETON      .  .             . .  . .             . .     288 

36.  EYES  AND  EYELETS  OF  BEE          . .             . .  . .             . .             289 

37.  EYE  OF  FLY            . .            . .            . .            . .  . .            . .     290 

38.  DIAGRAM  OF  MOSAIC  VISION         ..             ..  ..            ..            291 

39.  DiHECTION-BETINA     .  .                  .  .                   .  .                   .  .  .  .                  .  .       295 

40.  ANTENNARY  STRUCTURES  OF  HYMENOPTERA  297 


ANIMAL  LIFE  AND  INTELLIGENCE. 

CHAPTEE  I. 

THE   NATURE    OF   ANIMAL   LIFE. 

I  ONCE  asked  a  class  of  school-boys  to  write  down  for  me  in 
a  few  words  what  they  considered  the  chief  characteristics 
of  animals.  Here  are  some  of  the  answers — 

1.  Animals  move  about,  eat,  and  grow. 

2.  Animals  eat,  grow,  breathe,  feel  (at  least,  most  of 
them  do),  and  sleep. 

3.  Take  a  cat,  for  example.     It  begins  as  a  kitten;  it 
eats,  drinks,  plays  about,  and  grows  up  into  a  cat,  which 
does  much  the  same,  only  it  is  more  lazy,  and  stops  grow- 
ing.    At  last  it  grows  old  and  dies.    But  it  may  have 
kittens  first. 

4.  An  animal  has  a  head  and  tail,  -four  legs,  and  a 
body.     It  is  a  living  creature,  and  not  a  vegetable. 

5.  Animals  are  living  creatures,  made  of  flesh  and 
blood. 

Combining  these   statements,  we  have  the  following 
characteristics  of  animals  : — 

1.  Each  has  a  proper  and  definite  form,  at  present 
described  as  "  a  head  and  tail,  four  legs,  and  a  body." 

2.  They  breathe. 

3.  They  eat  and  drink. 

4.  They  grow. 

5.  They  also  "  grow  up."     The  kitten  grows  up  into  a 
cat,  which  is  somewhat  different  from  the  kitten. 

6.  They  move  about  and  sleep. 


Animal  Life  and  Intelligence. 


7.  They  feel — "  at  least  some  of  them  do." 

8.  They  are  made  of  "  flesh  and  blood." 

9.  They  grow  old  and  die. 

10.  They  reproduce  their  kind.     The   cat  may  have 
kittens. 

11.  They  are  living  organisms,  but  "  not  vegetables." 
Now,  let  us  look  carefully  at  these  characteristics,  all 

of  which  were  contained  in  the  five  answers,  and  were 
probably  familiar  in  some  such  form  as  this  to  all  the 
boys,  and  see  if  we  cannot  make  them  more  general  and 
more  accurate. 

1.  An  animal  has  a  definite  form.  My  school-boy  friend 
described  it  as  a  head  and  tail,  four  legs,  and  a  body.  But 
it  is  clear  that  this  description  applies  only  to  a  very  limited 
number  of  animals.  It  will  not  apply  to  the  butterfly,  with 
its  great  wings  and  six  legs ;  nor  to  the  lobster,  with  its 
eight  legs  and  large  pincer-claws ;  to  the  limbless  snake 
and  worm,  the  finned  fish,  the  thousand-legs,  the  oyster 
or  the  snail,  the  star-fish  or  the  sea-anemone.  The 
animals  to  which  my  young  friend's  description  applies 
form,  indeed,  but  a  numerically  insignificant  proportion 
of  the  multitudes  which  throng  the  waters  and  the  air, 
and  not  by  any  means  a  large  proportion  of  those  that 
walk  upon  the  surface  of  the  earth.  The  description 
applies  only  to  the  backboned  vertebrates,  and  not  to 
nearly  all  of  them. 

It  is  impossible  to  summarize  in  a  sentence  the  form- 
characteristics  of  animals.  The  diversities  of  form  are 
endless.  Perhaps  the  distinguishing  feature  is  the  pre- 
valence of  curved  and  rounded  contours,  which  are  in 
striking  contrast  to  the  definite  crystalline  forms  of  the 
inorganic  kingdom,  characterized  as  these  are  by  plane 
surfaces  and  solid  angles.  We  may  say,  however,  that  all 
but  the  very  lowliest  animals  have  each  and  all  a  proper 
and  characteristic  form  of  their  own,  which  they  have  in- 
herited from  their  immediate  ancestors,  and  which  they 
hand  on  to  their  descendants.  But  this  form  does  not 
remain  constant  throughout  life.  Sometimes  the  change 


The  Nature  of  Animal  Life. 


is  slight;  in  many  cases,  however,  the  form  alters  very 
markedly  during  the  successive  stages  of  the  life  of  the 
individual,  as  is  seen  in  the  frog,  which  begins  life  as  a 
tadpole,  and  perhaps  even  more  conspicuously  in  the 
butterfly,  which  passes  through  a  caterpillar  and  a  chry- 
salis stage.  Still,  these  changes  are  always  the  same  for 
the  same  kind  of  animal.  So  that  we  may  say,  each 
animal  has  a  definite  form  and  shape  or  series  of  shapes. 

2.  Animals  breathe.  The  essential  thing  here  is  that 
oxygen  is  taken  in  by  the  organism,  and  carbonic  acid  gas 
is  produced  by  the  organism.  No  animal  can  carry  on  its 
life-processes  unless  certain  chemical  changes  take  place 
in  the  substance  of  which  it  is  composed.  And  for  these 
chemical  changes  oxygen  is  essential.  The  products  of 
these  changes,  the  most  familiar  of  which  are  carbonic 
acid  gas  and  urea,  must  be  got  rid  of  by  the  process  of 
excretion.  Eespiration  and  excretion  are  therefore  essential 
and  characteristic  life-processes  of  all  animals. 

In  us,  and  in  all  air-breathing  vertebrates,  there  are 
special  organs  set  apart  for  respiration  and  excretion 
of  carbonic  acid  gas.  These  are 
the  lungs.  A  great  number  of 
insects  also  breathe  air,  but  in  a 
different  way.  They  have  no  lungs, 
but  they  respire  by  means  of  a 
number  of  apertures  in  their  sides, 
and  these  open  into  a  system  of  a/  c 
delicate  branching  tubes  which 
ramify  throughout  the  body.  Many 

organisms,    however,    such    as   fish    Fig.  1.—  Diagram  of  spiracles 

and  lobsters  and  molluscs,  breathe 


the  air  dissolved  in  the  water  in      The  skin,  etc.,  of  the  back  has 

.   .  been  removed,  and  the  crop   (cr.) 

Which  they  live.      The  Special  Organs    and    alimentary    canal    (al.c.)   dis- 

*  .  °  played.      The  air-tubes  are  repre- 

developed  for  this  purpose  are  the  8eiited  by  dotted  lines-    The  tei» 

A  spiracles  are  numbered  to  the  right 

gills.     They  are  freely  exposed  to  of  the  figure. 
the  water  from  which  they  abstract  the  air  dissolved  therein. 
When  the  air  dissolved  in  the  water  is  used  up,  they  sicken 
and  die.     There  can  be  nothing  more  cruel  than  to  keep 


Animal  Life  and  Intelligence. 


aquatic  animals  in  a  tank  or  aquarium  in  which  there  is 
no  means  of  supplying  fresh  oxygen,  either  by  the  action 
of  green  vegetation,  or  by  a  jet  of  water  carrying  down  air- 
bubbles,  or  in  some  other  way.  And  then  there  are  a 
number  of  animals  which  have  no  special  organs  set  apart 
for  breathing.  In  them  respiration  is  carried  on  by  the 
general  surface  of  the  body.  The  common  earthworm  is 


Fig.  2.— Gills  of  mussel. 

o.g.,  outer  gill ;  i.g.,  inner  gill;  mo.,  mouth ;  m.,  muscles  for  closing  shell ;  ma.,  mantle; 
*.,  shell;  /..  foot;  h.,  position  of  heart;  e.s.,  exhalent  siphon,  whence  the  water  passes  out 
from  the  gill-chamber ;  i.s.,  inhalent  eiphon,  where  the  water  enters. 

The  left  valve  of  the  shell  has  been  removed,  and  the  mantle  cut  away  along  the  dark  line. 

one  of  these ;  and  most  microscopic  organisms  are  in  the 
same  condition.  Still,  even  if  there  be  no  special  organs 
for  breathing,  the  process  of  respiration  must  be  carried  on 
by  all  animals. 

3.  They  eat  and  drink.  The  living  substance  of  an 
animal's  body  is  consumed  during  the  progress  of  those 
chemical  changes  which  are  consequent  upon  respiration ; 
and  this  substance  must,  therefore,  be  made  good  by 
taking  in  the  materials  out  of  which  fresh  life-stuff  can 
be  formed.  This  process  is  called,  in  popular  language, 
feeding.  But  the  food  taken  in  is  not  identical  with  the 
life-stuff  formed.  It  has  to  undergo  a  number  of  chemical 
changes  before  it  can  be  built  into  the  substance  of  the 
organism.  In  us,  and  in  all  the  higher  animals,  there  is 
a  complex  system  of  organs  set  aside  for  the  preparation, 
digestion,  and  absorption  of  the  food.  But  there  are 
certain  lowly  organisms  which  can  take  in  food  at  any 
portion  of  their  surface,  and  digest  it  in  any  part  of  their 


The  Nature  of  Animal  Life. 


substance.  One  of  these  is  the  amoeba,  a  minute  speck  of 
jelly-like  life-stuff,  which  lives  in  water,  and  tucks  in  a  bit 
of  food-material  just  as  it  comes.  And  there  are  certain 
degenerate  organisms  which  have  taken  to  a  parasitic  life, 
and  live  within  the  bodies  of  other  animals.  Many  of 
these  can  absorb  the  material  prepared  by  their  host 
through  the  general  surface  of  their  simple  bodies.  But 
here,  again,  though  there  may  be  no  special  organs  set 
apart  for  the  preparation,  absorption,  and  digestion  of 
food,  the  process  of  feeding  is  essential  to  the  life  of  all 
animals.  Stop  that  process  for  a  sufficient  length  of  time, 
and  they  inevitably  die. 

4.  They  grow.  Food,  as  we  have  just  seen,  has  to  be 
taken  in,  digested,  and  absorbed,  in  order  that  the  loss  of 
substance  due  to  the  chemical  changes  consequent  on 
respiration  may  be  made  good.  But  where  the  digestion 
and  absorption  are  in  excess  of  that  requisite  for  this 
purpose,  we  have  the  phenomenon  of  growth. 

What  are  the  characteristics  of  this  growth  ?  We 
cannot,  perhaps,  describe  it  better  than  by  saying  (1)  that 
it  is  organic,  that  is  to  say,  a  growth  of  the  various  organs 
of  the  animal  in  due  proportion;  (2)  that  it  takes  place, 
not  merely  by  the  addition  of  new  material  (for  a  crystal 
grows  by  the  addition  of  new  material,  layer  upon  layer), 
but  by  the  incorporation  of  that  new  material  into  the  very 
substance  of  the  old;  and  (3)  that  the  material  incor- 
porated during  growth  differs  from  the  material  absorbed 
from  without,  which  has  undergone  a  preparatory  chemical 
transformation  within  the  animal  during  digestion.  The 
growth  of  an  animal  is  thus  dependent  upon  the  continued 
absorption  of  new  material  from  without,  and  its  trans- 
formation into  the  substance  of  the  body. 

The  animal  is,  in  fact,  a  centre  of  continual  waste  and 
repair,  of  nicely  balanced  constructive  and  destructive 
processes.  These  are  the  invariable  concomitants  of  life. 
Only  so  long  as  the  constructive  processes  outbalance  the 
destructive  processes  does  growth  continue.  During  the 
greater  part  of  a  healthy  man's  life,  for  example,  the  two 


Animal  Life  and  Intelligence. 


processes,  waste  and  repair,  are  in  equilibrium.  In  old 
age,  waste  slowly  but  surely  gains  the  mastery ;  and  at 
death  the  balanced  process  ceases,  decomposition  sets  in, 
and  the  elements  of  the  body  are  scattered  to  the  winds  or 
returned  to  mother  earth. 

There  are  generally  limits  of  growth  which  are  not 
exceeded  by  any  individuals  of  each  particular  kind  of 
animal.  But  these  limits  are  somewhat  variable  among 
the  individuals  of  each  kind.  There  are  big  men  and 
little  men,  cart-horses  and  ponies,  bloodhounds  and  lap- 
dogs.  Wild  animals,  however,  when  fully  grown,  do  not 
vary  so  much  in  size.  The  period  of  growth  is  also 
variable.  Many  of  the  lower  backboned  animals  probably 
grow  during  the  whole  of  life,  but  those  which  suckle  their 
young  generally  cease  growing  after  a  fraction  (in  us  from 
one-fourth  to  one-fifth)  of  the  allotted  span  of  life  is 
past. 

5.  But  animals  not  only  grow — they  also  "grow  up." 
The  kitten  grows  up  into  a  cat,  which  is  somewhat  different 
from  the  kitten.  We  speak  of  this  growing  up  of  an  animal 
as  its  development.  The  proportion  of  the  various  parts 
and  organs  progressively  alter.  The  relative  lengths  of 
the  arms  and  legs,  and  the  relative  size  of  the  head,  are 
not  the  same  in  the  infant  as  in  the  man  or  woman.  Or, 
take  a  more  marked  case.  In  early  spring  there  is  plenty 
of  frog-spawn  in  the  ponds.  A  number  of  blackish  specks 
of  the  size  of  mustard  seeds  are  embedded  in  a  jelly-like 
mass.  They  are  frogs'  eggs.  They  seem  unorganized. 
But  watch  them,  and  the  organization  will  gradually 
appear.  The  egg  will  be  hatched,  and  give  rise  to  a  little 
fish-like  organism.  This  will  by  degrees  grow  into  a 
tadpole,  with  a  powerful  swimming  tail  and  rounded  h.ead 
and  body,  but  with  no  obvious  neck  between  them.  Legs 
will  appear.  The  tail  will  shrink  in  size  and  be  gradually 
drawn  into  the  body.  The  tadpole  will  have  developed 
into  a  minute  frog. 

There  are  many  of  the  lower  animals  which  go  through 
a  not  less  wonderful,  if  not  more  wonderful,  metamorphosis. 


The  Nature  of  Animal  Life. 


The  butterfly  or  the  silkworm  moth,  beginning  life  as  a 
caterpillar  and  changing  into  a  chrysalis,  from  which  the 
perfect  insect  emerges,  is  a  familiar  instance.  And  hosts 
of  the  marine  invertebrates  have  larval  forms  which  have 
but  little  resemblance  to  their  adult  parents. 

Such  a  series  of  changes  as  is  undergone  by  the  frog 
is  called  metamorphosis,  which  essentially  consists  in  the 
temporary  development  of  certain  provisional  embryonic 
organs  (such  as  gills  and  a  powerful  swimming  tail)  and 
the  appearance  of  adult  organs  (such  as  lungs  and  legs)  to 
take  their  place.  In  metamorphosis  these  changes  occur 
during  the  free  life  of  the  organism.  But  beneath  the 
eggshell  of  birds  and  within  the  womb  of  mammals 
scarcely  less  wonderful  changes  are  slowly  but  surely 
effected,  though  they  are  hidden  from  our  view.  There 
is  no  metamorphosis  during  the  free  life  of  the  organism, 
but  there  is  a  prenatal  transformation.  The  little  embryo 
of  a  bird  or  mammal  has  no  gills  like  the  tadpole  (though 
it  has  for  a  while  gill-slits,  pointing  unmistakably  to  its 
fishy  ancestry),  but  it  has  a  temporary  provisional 
breathing  organ,  called  the  allantois,  pending  the  full 
development  and  functional  use  of  its  lungs. 

All  the  higher  animals,  in  fact — the  dog,  the  chick,  the 
serpent,  the  frog,  the  fish,  the  lobster,  the  butterfly,  the 
worm,  the  star-fish,  the  mollusc,  it  matters  not  which  we 
select — take  their  origin  from  an  apparently  unorganized 
egg.  They  all,  therefore,  pass  during  their  growth  from  a 
comparatively  simple  condition  to  a  comparatively  complex 
condition  by  a  process  of  change  which  is  called  develop- 
ment. But  there  are  certain  lowly  forms,  consisting 
throughout  life  of  little  more  than  specks  of  jelly-like  life- 
stuff,  in  which  such  development,  if  it  occurs  at  all,  is  not 
conspicuous. 

6.  They  move  about  and  sleep.  This  is  true  of  our 
familiar  domestic  pets.  The  dog  and  the  cat,  after  periods 
of  restless  activity,  curl  themselves  up  and  sleep.  The 
canary  that  has  all  day  been  hopping  about  its  cage,  or 
perhaps  been  allowed  the  freedom  of  the  dining-room,  tucks 


8  Animal  Life  and  Intelligence. 

its  head  under  its  wing  and  goes  to  sleep.  The  cattle  in 
the  meadows,  the  sheep  in  the  pastures,  the  horses  in  the 
stahles,  the  birds  in  the  groves,  all  show  alternating  periods 
of  activity  and  repose.  But  is  this  true  of  all  animals  ? 
Do  all  animals  "  move  about  and  sleep  "  ?  The  sedentary 
oyster  does  not  move  about  from  place  to  place ;  the 
barnacle  and  the  coral  polyp  are  fixed  for  the  greater  part 
of  life ;  and  whether  these  animals  sleep  or  not  it  is  very 
difficult  to  say.  We  must  make  our  statement  more  com- 
prehensive and  more  accurate. 

If  we  throw  it  into  the  following  form,  it  will  be  more 
satisfactory  :  Animals  exhibit  certain  activities  ;  and 
periods  of  activity  alternate  with  periods  of  repose. 

I  shall  have  more  to  say  hereafter  concerning  the 
activities  of  animals.  Here  I  shall  only  say  a  few  words 
concerning  the  alternating  periods  of  repose.  No  organism 
can  continue  in  ceaseless  activity  unbroken  by  any  inter- 
vening periods  of  rest.  Nor  can  the  organs  within  an 
organism,  however  continuous  their  activity  may  appear, 
work  on  indefinitely  and  unrestfully.  The  heart  is  appa- 
rently restless  in  its  activity.  But  in  every  five  minutes 
of  the  continued  action  of  the  great  force-pump  (ventricle) 
of  the  heart,  two  only  are  occupied  in  the  efforts  of  con- 
traction and  work,  while  three  are  devoted  to  relaxation 
and  repose.  What  we  call  sleep  may  be  regarded  as  the 
repose  of  the  higher  brain-centres  after  the  activity  of  the 
day's  work — a  repose  in  which  the  voluntary  muscles  share. 

The  necessity  for  rest  and  repose  will  be  readily  under- 
stood. We  have  seen  that  the  organism  is  a  centre  of 
waste  and  repair,  of  nicely  balanced  destructive  and  recon- 
structive processes.  Now,  activity  is  accompanied  by 
waste  and  destruction.  But  it  is  clear  that  these  processes, 
by  which  the  substance  of  the  body  and  its  organs  is  used 
up,  cannot  go  on  for  an  indefinite  period.  There  must 
intervene  periods  of  reconstruction  and  recuperation. 
Hence  the  necessity  of  rest  and  repose  alternating  with 
the  periods  of  more  or  less  prolonged  activity. 

7.   They  feel — "  at  least  some  of  them  do"     The  quali- 


The  Nature  of  Animal  Life. 


fication  was  a  wise  one,  for  in  truth,  as  we  shall  hereafter 
see,  we  know  very  little  about  the  feelings  of  the  lower 
organisms.  The  one  animal  of  whose  feelings  I  know 
anything  definite  and  at  first  hand,  is  myself.  Of  course, 
I  believe  in  the  feelings  of  others  ;  but  when  we  come  to 
very  lowly  organisms,  we  really  do  not  know  whether 
they  have  feelings  or  not,  or,  if  they  do,  to  what  extent 
they  feel. 

Shall  we  leave  this  altogether  out  of  account  ?  Or  can 
we  throw  it  into  some  form  which  is  more  general  and  less 
hypothetical  ?  This,  at  any  rate,  we  know — that  all  animals, 
even  the  lowest,  are  sensitive  to  touches,  sights,  or  sounds. 
It  is  a  matter  of  common  observation  that  their  activities 
are  generally  set  agoing  under  the  influence  of  such  sugges- 
tions from  without.  Perhaps  it  will  be  objected  that  there 
is  no  difference  between  feeling  and  being  sensitive.  But 
I  am  using  the  word  "  sensitive  "  in  a  general  sense — in 
that  sense  in  which  the  photographer  uses  it  when  he 
speaks  of  a  sensitive  plate,  or  the  chemist  when  he  speaks 
of  a  sensitive  test.  When  I  say  that  animals  are  sensitive, 
I  mean  that  they  answer  to  touches,  or  sounds,  or  other 
impressions  (what  are  called  stimuli)  coming  from  without. 
They  may  feel  or  not ;  many  of  them  undoubtedly  do.  But 
that  is  another  aspect  of  the  sensitiveness.  Using  the 
term,  then,  with  this  meaning,  we  may  say,  without  quali- 
fication, that  all  animals  are  more  or  less  sensitive  to 
external  influences. 

8.  They  are  made  of  "  flesh  and  blood.'1  Here  we  have 
allusion  to  the  materials  of  which  the  animal  body  is  com- 
posed. It  is  obviously  a  loose  and  unsatisfactory  statement 
as  it  stands.  An  American  is  said  to  have  described  the 
difference  between  vertebrates  and  insects  by  saying  that 
the  former  are  composed  of  flesh  and  bone,  and  the  latter  of 
skin  and  squash.  But  even  if  we  amend  the  statement  that 
animals  are  made  of  "  flesh  and  blood  "  by  the  addition  of 
the  words,  "  or  of  skin  and  squash,"  we  shall  hardly  have  a 
sufficiently  satisfactory  statement  of  the  composition  of  the 
animal  body. 


10  Animal  Life  and  Intelligence. 

The  essential  constituent  of  animal  (as  indeed  also  of 
vegetable)  tissues  is  protoplasm.  This  is  a  nearly  colour- 
less, jelly-like  substance,  composed  of  carbon,  hydrogen, 
nitrogen,  and  oxygen,  with  some  sulphur  and  phosphorus, 
and  often,  if  not  always,  some  iron  ;  and  it  is  permeated 
by  water.  Protoplasm,  together  with  certain  substances, 
such  as  bony  and  horny  matter,  which  it  has  the  power 
of  producing,  constitutes  the  entire  structure  of  simple 
organisms,  and  is  built  up  into  the  organs  of  the  bodies 
of  higher  animals.  Moreover,  in  these  organs  it  is  not 
arranged  as  a  continuous  mass  of  substance,  but  is  dis- 
tributed in  minute  separate  fragments,  or  corpuscles,  only 
visible  under  the  microscope,  called  cells.  These  cells  are 
of  very  various  shapes — spherical,  discoidal,  polyhedral, 
columnar,  cubical,  flattened,  spindle-shaped,  elongated,  and 
stellate. 

A  great  deal  of  attention  has  been  devoted  of  late  years 
to  the  minute  structure  of  cells,  and  the  great  improvements 
in  microscopical  powers  and  appliances  have  enabled 
investigators  to  ascertain  a  number  of  exceedingly  inte- 
resting and  important  facts.  The  external  surface  of  a  cell 
is  sometimes,  but  not  always  in  the  case  of  animals,  bounded 
by  a  film  or  membrane.  Within  this  membrane  the  sub- 
stance of  the  cell  is  made  up  of  a  network  of  very  delicate 
fibres  (the  plasmogen),  enclosing  a  more  fluid  material  (the 
plasm) ;  and  this  network  seems  to  be  the  essential  living 
substance.  In  the  midst  of  the  cell  is  a  small  round  or 
oval  body,  called  the  nucleus,  which  is  surrounded  by  a  very 
delicate  membrane,  In  this  nucleus  there  is  also  a  net- 
work of  delicate  plasmogen  fibres,  enclosing  a  more  fluid 
plasm  material.  At  certain  times  the  network  takes  the 
form  of  a  coiled  filament  or  set  of  filaments,  and  these 
arrange  themselves  in  the  form  of  rosettes  and  stars.  In 
the  meshwork  of  the  net  or  in  the  coils  of  the  filament 
there  may  be  one  or  more  small  bodies  (nucleoli),  which 
probably  have  some  special  significance  in  the  life  of  the 
cell.  These  cells  multiply  or  give  birth  to  new  cells  by 
dividing  into  two,  and  this  process  is  often  accompanied 


The  Nature  of  Animal  Life. 


1 1 


by  special  changes  in  the  nucleus  (which  also  divides)  and 
by  the  arrangement  of  its  network  or  filaments  into  the 
rosettes  and  stars  before  alluded  to. 

Instead,  therefore,  of  the  somewhat  vague  statement 
that  animals  are  made  of  flesh  and  blood,  we  may  now  sayj 
that  the  living  substance  of  which  animals  are  composed! 
is  a  complex  material  called  protoplasm ;  that  organisms 
are  formed  either  of  single  cells  or  of  a  number  of  related 
cells,  together  with  certain  life-products  of  these  cells  ;  and 


Fig.  3.— A  cell,  greatly  magnified. 

c.m.,  cell-membrane;  c.p.,  cell-protoplasm  ;  n.m.,  nuclear  membrane ;  n.p.,  nuclear  proto- 
plasm ;  n./.,  coiled  nuclear  filament. 

that  each  cell,  small  as  it  is,  has  a  definite  and  wonderful 
minute  structure  revealed  by  the  microscope. 

9.  Animals  grow  old  and  die.  This  is  a  familar  obser- 
vation. Apart  from  the  fact  that  they  are  often  killed  by 
accident,  by  the  teeth  or  claws  of  an  enemy,  or  by  disease, 
animals,  like  human  beings,  in  course  of  time  become  less 
active  and  less  vigorous  ;  the  vital  forces  gradually  fail, 
and  eventually  the  flame  of  life,  which  has  for  some  time 
been  burning  dimmer  and  dimmer,  flickers  out  and  dies. 
But  is  this  true  of  all  animals  ?  Can  we  say  that  death — 
as  distinct  from  being  killed — is  the  natural  heritage  of 
every  creature  that  lives  ? 


12 


Animal  Life  and  Intelligence. 


One  of  the  simplest  living  creatures  is  the  amoeba.  It 
consists  of  a  speck  of  nucleated  protoplasm,  no  larger  than 
a  small  pin's  head.  Simple  as  it  is,  all  the  essential  life- 
processes  are  duly  performed.  It  is  a  centre  of  waste  and 
repair;  it  is  sensitive  and  responsive  to  a  stimulus ;  respi- 
ration and  nutrition  are  effected  in  a  simple  and  primitive 
fashion.  It  is,  moreover,  reproductive.  First  the  nucleus 
and  then  the  protoplasm  of  the  cell  divide,  and  in  place  of 
one  amoeba  there  are  two.  And  these  two  are,  so  far  as 
we  can  tell,  exactly  alike.  There  is  no  saying  which  is 
mother  and  which  is  daughter ;  and,  so  far  as  we  can  see 
at  present,  there  is  no  reason  why  either  should  die.  It  is 
conceivable  that  amoebae  never  die,  though  they  may  be 
killed  in  immense  numbers.  Hence  it  has  been  plausibly 


c.v. 


n. 


Fig.  4. — Amoeba. 

1.  An  amoeba,  showing  the  inner  and  outer  substance  (endosarc  and  ectosarc) ;  a  pseudo- 
podium,  p.s. ;  the  nucleus,  n. ;  and  the  contractile  vesicle,  c.v.  2.  An  amoeba  dividing  into 
two.  3.  The  division  just  effected. 

maintained  that  the  primitive  living  cell  is  by  nature 
deathless :  that  death  is  not  the  heritage  of  all  living 
things ;  that  death  is  indeed  an  acquisition,  painful  indeed 
to  the  individual,  but,  since  it  leaves  the  stage  free  for  the 
younger  and  more  vigorous  individuals,  conducive  to  the 
general  good. 

In  face  of  this  opinion,  therefore,  we  cannot  say  that 
all  animals  grow  old  and  die ;  but  we  may  still  say  that 
all  animals,  with  the  possible  exception  of  some  of  the 
lowest  and  simplest,  exhibit,  after  a  longer  or  a  shorter 
time,  a  waning  of  the  vital  energies  which  sooner  or  later 
ends  in  death. 

10.  Animals  reproduce  their  kind.     We  have  just  seen 


The  Nature  of  Animal  Life.  13 

the  nature  of  reproduction  in  the  simple  unicellular  amoeba. 
The  reproduction  of  the  constituent  cells  in  the  complex 
multicellular  organism,  during  its  natural  growth  or  to 
make  good  the  inevitable  loss  consequent  on  the  wear  and 
tear  of  life,  is  of  the  same  character. 

When  we  come  to  the  higher  organisms,  reproduction 
is  effected  by  the  separation  of  special  cells  called  egg-cells, 
or  ova,  from  a  special  organ  called  the  ovary ;  and  these, 
in  a  great  number  of  cases,  will  not  develop  into  a  new 
organism  unless  they  be  fertilized  by  the  union  with  them 
in  each  case  of  another  cell — the  sperm-cell — produced  by  a 
different  individual.  The  separate  parents  are  called  male 


I 


Fig.  5. — Egg-cell  and  sperm-cell, 
o,  ovum  or  egg;  &,  spermatozoon  or  sperm. 

and  female,  and  reproduction  of  this  kind  is  said  to  be 
sexual. 

The  wonderful  thing  about  this  process  is  the  power  of 
the  fertilized  ovum,  produced  by  the  union  of  two  minute 
cells  from  different  parents,  to  develop  into  the  likeness  of 
these  parents.  This  likeness,  however,  though  it  extends 
to  minute  particulars,  is  not  absolute.  The  offspring  is  not 
exactly  like  either  parent,  nor  does  it  present  a  precise 
mean  between  the  characters  of  the  two  parents.  There 
is  always  some  amount  of  individual  var^iljty,  the  effects 
of  which,  as  we  shall  hereafter  see,  are  of  wide  importance. 
We  are  wont  to  say  that  these  phenomena,  the  transmis- 
sion of  parental  characteristics,  together  with  a  margin  of 


14  Animal  Life  and  Intelligence. 

difference,  are  due  to  heredity  with  variation.  But  this 
merely  names  the  facts.  How  the  special  reproductive 
cells  have  acquired  the  secret  of  developing  along  special 
lines,  and  reproducing,  with  a  margin  of  variability,  the 
likeness  of  the  organisms  which  produced  them,  is  a  matter 
concerning  which  we  can  at  present  only  make  more  or 
less  plausible  guesses. 

Scarcely  less  wonderful  is  the  power  which  separated 
bits  of  certain  organisms,  such  as  the  green  freshwater 
hydra  of  our  ponds,  possess  of  growing  up  into  the  com- 
plete organism.  Cut  a  hydra  into  half  a  dozen  fragments, 
and  each  fragment  will  become  a  perfect  hydra.  Repro- 
duction of  this  kind  is  said  to  be  asexual. 

We  shall  have,  in  later  chapters,  to  discuss  more  fully 
some  of  the  phenomena  of  reproduction  and  heredity. 
For  the  present,  it  is  sufficient  to  say  that  animals  repro- 
duce their  kind  by  the  detachment  of  a  portion  of  the 
substance  of  their  own  bodies,  which  portion,  in  the  case 
of  the  higher  animals,  undergoes  a  series  of  successive 
developmental  changes  constituting  its  life-history,  the 
special  nature  of  which  is  determined  by  inheritance,  and 
the  result  of  which  is  a  new  organism  in  all  essential 
respects  similar  to  the  parent  or  parents. 

11.  Animals  are  living  organisms,  and  "not  vegetables." 
The  first  part  of  this  final  statement  merely  sums  up  the 
characteristics  of  living  animals  which  have  gone  before. 
But  the  latter  part  introduces  us  to  the  fact  that  there  are 
other  living  organisms  than  those  we  call  animals,  namely, 
those  which  belong  to  the  vegetable  kingdom. 

It  might,  at  first  sight,  be  thought  a  very  easy  matter 
to  distinguish  between  animals  and  plants.  There  is  no 
chance,  for  example,  of  mistaking  to  which  kingdom  an 
oak  tree  or  a  lion,  a  cabbage  or  a  butterfly,  belongs.  But 
when  we  come  down  to  the  simpler  organisms,  those  whose 
bodies  are  constituted  by  a  single  cell,  the  matter  is  by  no 
means  so  easy.  There  are,  indeed,  lowly  creatures  which 
are  hovering  on  the  boundary-line  between  the  two 
kingdoms.  We  need  not  discuss  the  nature  of  these 


The  Natiire  of  Animal  Life. 


boundary  forms.  It  is  sufficient  to  state  that  unicellular 
plants  are  spoken  of  as  protophyta,  and  unicellular  animals 
as  protozoa,  the  whole  group  of  unicellular  organisms  being 
classed  together  as  protista.  The  animals  whose  bodies 
are  formed  of  many  cells  in  which  there  is  a  differentiation 
of  structure  and  a  specialization  of  function,  are  called 
metazoa,  and  the  multicellular  plants  metaphyta.  The  re- 
lations of  these  groups  may  be  thus  expressed — 

Animals.  Plants. 


Metazoa.        Protozoa.  Protophyta.        Metaphyta. 

Protista. 

There  are  three  matters  with  regard  to  the  life-process 
of  animals  and  plants  concerning  which  a  few  words  must 
be  said.  These  are  (1)  their  relation  to  food-stuffs ;  (2) 
their  relation  to  the  atmosphere;  (3)  their  relation  to 
energy,  or  the  power  of  doing  work. 

With  regard  to  the  first  matter,  that  of  food-relation, 
the  essential  fact  seems  to  be  the  dependence  of  animals 
on  plants.  Plants  can  manufacture  protoplasm  out  of  its 
constituents  if  presented  to  them  in  suitable  inorganic 
form  scattered  through  earth  and  air  and  water.  Hence 
the  peculiar  features  of  their  form,  the  branching  and 
spreading  nature  of  those  parts  which  are  exposed  to  the 
air,  and  the  far-reaching  ramifications  of  those  parts 
which  are  implanted  in  the  earth.  Hence,  too,  the  flattened 
leaves,  with  their  large  available  surface.  Animals^jarfi. 
unable  to  manufacture  protoplasm  in  this  way.  They 
are,  sooner  or  later,  dependent  for  food  on  plant-products. 
It  is  true  that  the  carnivora  eat  animal  food,  but  the 
animals  they  eat  are  directly  or  indirectly  consumers  of 
vegetable  products.  Plants  are  nature's  primary  producers 
of  organic  material.  '  AnimaTTlifilize  these  products  and 
carry  them  to  higher  developments. 

In  relation  to  the  atmosphere,  animals  require  a  very 
much  larger  quantity  of  oxygen  than  do  plants.  This, 
during  the  respiratory  process,  combines  with  carbon  so 


1 6  Animal  Life  and  Intelligence. 

as  to  form  carbonic  acid  gas ;  and  the  atmosphere  would 
be  gradually  drained  of  its  oxygen  and  flooded  with  car- 
bonic acid  gas  were  it  not  that  plants,  through  their  green 
colouring  matter  (chlorophyll),  under  the  influence  of  light, 
have  the  power  of  decomposing  the  carbonic  acid  gas, 
seizing  on  the  carbon  and  building  it  into  their  tissues, 
and  setting  free  the  oxygen.  Thus  are  animals  and  green 
plants  complementary  elements  in  the  scheme  of  nature.* 
The  animal  eats  the  carbon  elaborated  by  the  plant  into 
organic  products  (starch  and  others),  and  breathes  the 
oxygen  which  the  plant  sets  free  after  it  has  abstracted 
the  carbon.  In  the  animal's  body  the  carbon  and 
oxygen  recombine ;  its  varied  activities  are  thus  kept 
going;  and  the  resultant  carbonic  acid  gas  is  breathed 
forth,  to  be  again  separated  by  green,  growing  plants  into 
carbonaceous  food-stuff  and  vitalizing  oxygen.  It  must 
be  remembered,  however,  that  vegetable  protoplasm,  like 
animal  protoplasm,  respires  by  the  absorption  of  oxygen 
and  the  formation  of  carbonic  acid  gas.  But  in  green 
plants  this  process  is  outbalanced  by  the  characteristic 
action  of  the  chlorophyll,  by  which  carbonic  acid  gas  is 
decomposed. 

Lastly,  we  have  to  consider  the  relations  of  animals  and 
plants  to  energy.  Energy  is  denned  as  the  power  of  doing 
work,  and  it  is  classified  by  physicists  under  two  modes — 
potential  energy,  or  energy  of  position ;  and  kinetic  energy, 
or  energy  of  motion.  The  muscles  of  my  arm  contain 
a  store  of  potential  energy.  Suppose  I  pull  up  the  weight 

*  An  interesting  problem  concerning  the  atmosphere  is  suggested  by 
certain  geological  facts.  In  our  buried  coal-seams  and  other  carbonaceous 
deposits  a  great  quantity  of  carbon,  for  the  most  part  abstracted  from  the 
atmosphere,  has  been  stored  away.  Still  greater  quantities  of  carbon  are 
imprisoned,  in  the  substance  of  our  limestones,  which  contain,  when  pure, 
44  per  cent,  of  this  element.  A  large  quantity  of  oxygen  lias  also  been  taken 
from  the  atmosphere  to  combine  with  other  elements  during  their  oxidation. 
The  question  is — Was  the  atmosphere,  in  the  geological  past,  more  richly  laden 
with  carbonic  acid  gas,  of  which  some  has  entered  into  combination  with  lime 
to  form  limestone,  while  some  has  been  decomposed  by  plants,  the  carbon 
being  buried  as  coal,  and  the  oxygen  as  products  of  oxidation?  Or,  has  the 
atmosphere  been  furnished  with  continuous  fresh  supplies  of  carbonic  acid 
gas? 


The  Nature  of  Animal  Life.  1 7 


of  an  old-fashioned  eight-day  clock.  Some  of  the 
energy  of  my  arm  is  converted  into  the  potential  energy  of 
the  weight ;  that  is,  the  raised  weight  is  now  in  a  position 
of  advantage,  and  capable  of  doing  work.  It  has  energy  of 
position,  or  potential  energy.  If  the  chain  breaks,  down  falls 
the  weight,  and  exhibits  the  energy  of  motion.  But,  under 
ordinary  circumstances,  this  potential  energy  is  utilized  in 
giving  a  succession  of  little  pushes  to  the  pendulum  to 
keep  up  its  swing,  and  in  overcoming  the  friction  of  the 
works.  Again,  the  energy  of  an  electric  current  may  be 
utilized  in  decomposing  water,  and  tearing  asunder  the 
oxygen  and  hydrogen  of  which  it  is  composed.  The 
oxygen  and  hydrogen  now  have  potential  energy,  and,  if 
they  be  allowed  to  combine,  this  will  manifest  itself  as  the 
light  and  heat  of  the  explosion.  These  examples  will 
serve  to  illustrate  the  nature  of  the  changes  which  energy 
undergoes.  These  are  of  the  nature  of  transferences  of 
energy  from  one  body  to  another,  and  of  transformations 
from  one  mode  or  manifestation  to  another.  The  most 
important  point  that  has  been  established  during  this 
century  with  regard  to  energy  is  that,  throughout  all  its 
transferences  and  transformations,  it  can  be  neither  created 
nor  destroyed.  But  there  is  another  point  of  great  im- 
portance. Transformations  of  energy  take  place  more 
readily  in  certain  directions  than  in  others.  And  there  is 
always  a  tendency  for  energy  to  pass  from  the  higher  or 
more  readily  transformable  to  the  lower  or  less  readily 
transformable  forms.  When,  for  example,  energy  has 
passed  to  the  low  kinetic  form  of  the  uniformly  distributed 
molecular  motion  of  heat,  it  is  exceedingly  difficult,  or 
practically  impossible,  to  transform  it  into  a  higher  and 
more  available  form. 

Now,  both  animals  and  plants  are  centres  of  the  trans- 
formation of  energy ;  and  in  them  energy,  notwithstanding 
that  it  is  being  raised  to  a  high  position  of  potentiality,  is 
constantly  tending  to  be  degraded  to  lower  forms.  Hence 
the  necessity  of  some  source  from  which  fresh  stores  of 
available  energy  may  be  constantly  supplied.  Such  a 


1 8  Animal  Life  and  Intelligence. 

source  is  solar  radiance.  This  it  is  which  gives  the 
succession  of  little  pushes  which  keeps  the  pendulum  of 
life  a-swinging.  And  it  is  the  green  plants  which,  through 
their  chlorophyll,  are  in  the  best  position  to  utilize  the 
solar  energy.  They  utilize  it  in  building  up,  from  the 
necessary  constituents  diffused  through  the  atmosphere 
and  the  soil,  complex  forms  of  organic  material,  of  which 
the  first  visible  product  seems  to  be  starch  ;  and  these  not 
only  contain  large  stores  of  potential  energy,  but  are 
capable,  when  combined  with  oxygen,  of  containing  yet 
larger  stores.  The  animal,  taking  into  its  body  these 
complex  materials,  and  elaborating  them  together  with 
oxygen  into  yet  more  complex  and  more  unstable  com- 
pounds, then,  during  its  vital  activity,  makes  organized 
use  of  the  transformation  of  the  potential  energy  thus 
stored  into  lower  forms  of  energy.  Thus  there  go  on  side 
by  side,  in  both  animals  and  plants,  a  building  up  or 
synthesis  of  complex  and  unstable  chemical  compounds, 
accompanied  by  a  storage  of  potential  energy,  and  a 
breaking  down  or  analysis  of  these  compounds  into  lower 
,  and  simpler  forms,  accompanied  by  a  setting  free  of  kinetic 
energy.  But  in  the  plant,  synthetic  changes  and  storage 
of  energy  are  in  excess,  while  in  the  animal,  analytic 
changes  and  the  setting  free  of  kinetic  energy  are  more 
marked.  Hence  the  variety  and  volume  of  animal  activities. 
The  building  up  of  complex  organic  substances  with 
abundance  of  stored  energy  may  be  roughly  likened  to  the 
building  up,  by  the  child  with  his  wooden  bricks,  of  houses 
and  towers  and  pyramids.  The  more  complex  they  become 
the  more  unstable  they  are,  until  a  touch  will  shatter  the 
edifice  and  liberate  the  stored-up  energy  of  position 
acquired  by  the  bricks.  Thus,  under  the  influence  of 
solar  energy,  do  plants  build  up  their  bricks  of  hydrogen, 
carbon,  and  oxygen  into  complex  molecular  edifices. 
Animals  take  advantage  of  the  structures  so  elaborated, 
modify  them,  add  to  them,  and  build  yet  more  complex 
molecular  edifices.  These,  at  the  touch  of  the  appropriate 
stimulus,  topple  over  and  break  down — not,  indeed,  into 


The  Nature  of  Animal  Life.  19 

the  elemental  bricks,  but  into  simpler  molecular  forms,  and 
these  again  in  later  stages  into  yet  simpler  forms,  which 
are  then  got  rid  of  or  excreted  from  the  body.  Meanwhile 
the  destructive  fall  of  the  molecular  edifice  is  accompanied 
by  the  liberation  of  energy — as  heat,  maintaining  the 
warmth  of  the  body;  as  visible  or  hidden  movements,  in 
locomotion,  for  example,  and  the  heart-beat;  and  some- 
times as  electrical  energy  (in  electric  fishes) ;  as  light  (in 
phosphorescent  animals  and  the  glow-worm),  or  as  sound. 
It  is  this  abundant  liberation  of  energy,  giving  rise  to 
many  and  complex  activities,  which  is  one  of  the  dis- 
tinguishing features  of  animals  as  compared  with  plants. 

We  have  now,  I  trust,  extended  somewhat  and  rendered 
somewhat  more  exact  our  common  and  familiar  knowledge 
of  the  nature  of  animal  life.  In  the  next  chapter  we  will 
endeavour  to  extend  it  still  further  by  a  consideration  of 
the  process  of  life. 


2O  Animal  Life  and  Intelligence. 


CHAPTER  II. 

THE    PROCESS   OF   LIFE. 

IN  the  foregoing  chapter,  on  "  The  Nature  of  Animal  Life," 
we  have  seen  that  animals  breathe,  feed,  grow,  are  sensitive, 
exhibit  various  activities,  and  reproduce  their  kind.  These 
may  be  regarded  as  primary  life-processes,  in  virtue  of 
which  the  animal  characterized  by  them  is  a  living 
creature.  We  have  now  to  consider  some  of  these  life- 
processes — the  sum  of  which  we  may  term  the  process  of 
life — a  little  more  fully  and  closely. 

The  substance  that  exhibits  these  life-processes  is 
protoplasm,  which  exists  in  minute  separate  masses 
termed  cells.  It  seems  probable,  however,  that  these 
cells,  separate  as  they  seem,  are  in  some  cases  united  to 
each  other  by  minute  protoplasmic  filaments.  In  the 
higher  animals  the  cells  in  different  parts  of  the  body 
take  on  different  forms  and  perform  different  functions. 
Like  cells  with  like  functions  are  also  aggregated  together 
into  tissues.  Thus  the  surfaces  of  the  body,  external  and 
internal,  are  bounded  by  or  lined  with  epithelial  tissue  ; 
the  bones  and  framework  of  the"  body  are  composed  of 
skeletal  tissue ;  nervous  tissue  goes  to  form  the  brain 
and  nerves;  contractile  tissue  is  found  in  the  muscles; 
while  the  blood  and  lymph  form  a  peculiar  nutritive  tissue. 
The  organs  of  the  body  are  distinct  parts  performing 
definite  functions,  such  as  the  heart,  stomach,  or  liver. 
An  organ  may  be  composed  of  several  tissues.  Thus  the 
heart  has  contractile  tissue  in  its  muscular  walls, 
epithelial  tissue  lining  its  cavities,  and  skeletal  tissue 
forming  its  framework.  Still,  notwithstanding  their  aggre- 


The  Process  of  Life.  2 1 

gation  into  tissues  and  organs,  it  remains  true  that  the  hody 
of  one  of  the  higher  animals  is  composed  of  cells,  together 
with  certain  cell-products,  horny,  calcareous,  or  other. 
The  simplest  animals,  called  protozoa,  are,  however,  uni- 
cellular, each  organism  being  constituted  by  a  single  cell. 

We  must  notice  that,  even  during  periods  of  apparent 
inactivity — for  example,  during  sleep — many  life-processes 
are  still  in  activity,  though  the  vigour  of  action  may  be 
somewhat  reduced.  When  we  are  fast  asleep,  respiration, 
the  heart-beat,*  and  the  onward  propulsion  of  food  through 
the  alimentary  canal,  are  still  going  on.  Even  at  rest,  the 
living  animal  is  a  going  machine.  In  some  cases,  however, 
as  during  the  hibernating  sleep  of  the  dormouse  or  the 
bear,  the  vital  activities  fall  to  the  lowest  possible  ebb. 
Moreover,  in  some  cases,  the  life-processes  may  be  tem- 
porarily arrested,  but  again  taken  up  when  the  special 
conditions  giving  rise  to  the  temporary  arrest  are  removed. 
Frogs,  for  example,  have  been  frozen,  but  have  resumed 
their  life-activities  when  subsequently  thawed. 

Let  us  take  the  function  of  respiration  as  a  starting- 
point  in  further  exemplification  of  the  nature  of  the 
life-processes  of  animals. 

The  organs  of  respiration,  in  ourselves  and  all  the 
mammalia,  are  the  lungs,  which  lie  in  the  thoracic  cavity 
of  the  chest,  the  walls  of  which  are  bounded  by  the  ribs 
and  breast-bone,  its  floor  being  formed  of  a  muscular  and 
movable  partition,  the  diaphragm,  which  separates  it  from 
the  stomach  and  other  alimentary  viscera  in  the  abdominal 
region.  The  lungs  fit  closely,  on  either  side  of  the  heart, 
in  this  thoracic  cavity ;  and  when  the  size  of  this  cavity  is 
altered  by  movements  of  the  ribs  and  diaphragm,  air  is 
either  sucked  into  or  expelled  from  the  lungs  through  the 
windpipe,  which  communicates  with  the  exterior  through 
the  mouth  or  nostrils.  It  is  unnecessary  to  describe 

*  It  has  before  been  noticed  that  the  organs  themselves  have  their 
periods  of  rest.  The  rhythm  of  rest  and  repose  in  the  heart  is  not  that  of 
the  activity  and  sleep  of  the  organism,  but  that  of  the  contraction  and 
relaxation  of  the  organ  itself. 


22  Animal  Life  and  Intelligence. 

the  minute  structure  of  the  lungs ;  suffice  it  to  say  that, 
in  the  mammal,  they  contain  a  vast  number  of  tubes,  all 
communicating  eventually  with  the  windpipe,  and  terminat- 
ing in  little  expanded  sacs  or  bags.  Around  these  little 
sacs  courses  the  blood  in  a  network  of  minute  capillary 
vessels,  the  walls  of  which  are  so  thin  and  delicate  that 
the  fluid  they  contain  is  only  separated  from  the  gas 
within  the  sacs  by  a  film  of  organic  tissue. 

The  blood  is  a  colourless  fluid,  containing  a  great 
number  of  round  red  blood-discs,  which,  from  their  minute 
size  and  vast  numbers,  seem  to  stain  it  red.  They  may 
be  likened  to  a  fleet  of  little  boats,  each  capable  of  being 
laden  with  a  freight  of  oxygen  gas,  while  the  stream  in 
which  they  float  is  saturated  with  carbonic  acid  gas.  This 
latter  escapes  into  the  air-sacs  as  the  fluid  courses  through 
the  delicate  capillary  tubes. 

Whither  goes  the  oxygen  ?  Whence  comes  the  carbonic 
acid  gas?  The  answer  to  these  questions  is  found  by 
following  the  course  of  the  blood-circulation.  The  pro- 
pulsion of  the  blood  throughout  the  body  is  effected  by  the 
heart,  an  organ  consisting,  in  mammals,  of  two  receivers 
(auricles)  into  which  blood  is  poured,  and  two  powerful 
force-pumps  (ventricles),  supplied  with  blood  from  the 
receivers  and  driving  it  through  great  arteries  to  various 
parts  of  the  body.  There  are  valves  between  the  receivers 
and  the  force-pumps  and  at  the  commencement  of  the 
great  arterial  vessels,  which  ensure  the  passage  of  the 
blood  in  the  right  direction.  The  two  receivers  lie  side  by 
.side ;  the  two  force-pumps  form  a  single  muscular  mass ; 
and  all  four  are  bound  up  into  one  organ;  but  there  is, 
during  adult  life,  no  direct  communication  between  the 
right  and  left  receivers  or  the  right  and  left  force-pumps. 

Let  us  now  follow  the  purified  stream,  with  its  oxygen- 
laden  blood-discs,  as  it  leaves  the  capillary  tubes  of  the 
lungs.  It  generally  collects,  augmented  by  blood  from 
other  similar  vessels,  into  large  veins,  which  pour  their 
contents  into  the  left  receiver.  Thence  it  passes  on  into 
the  left  force-pump,  by  which  it  is  propelled,  through  a 


The  Process  of  Life. 


great  arterial  vessel  and  the  numerous  branches  it  gives 
off,  to  the  head  and  brain,  to  the  body  and  limbs,  to  the 
abdominal  viscera ;    in   short,  to   all  parts  of  the   body 
except  the  lungs.      In  all  the   parts   thus  supplied,  the 
vessels  at  length  break  up  into  a  delicate  capillary  net- 
work, so  that  the  blood-fluid  is  se- 
parated from  the  tissue-cells  only 
by  the  delicate  organic  film  of  the 
capillary  walls.     Then   the   blood 
begins  to  re-collect  into  larger  and 
larger  veins.     But  a  change  has 
taken  place ;   the  blood-discs  have 
delivered  up  to  the  tissues  their 
freight  of  oxygen;   the  stream  in 
which  they  float  has  been  charged 
with  carbonic  acid  gas.     The  veins 
leading  from  various  parts  of  the 
body  converge  upon  the  heart  and 
pour  their  contents  into  the  right 
receiver;    thence  the  blood  passes 
into  the  right  force-pump,  by  which 
it  is  propelled,  by  arteries,  to  the  i.OeVtTemridT;  ~a.r^pm^r 

r      £  '      J  plexus  of  the  head ;    S.,  capillary 

lUngS.        There    the     blOOd-dlSCS    are    plexusofthebody;A.C'.>alimentary 

7  .  canal;  Lr.,  liver ;  R.A.,  right  auricle 

again  laden  with  oxygen,  the  stream  °f  the  heart ;  R- T-  risht  ventricle ; 
is  again  purified  of  its  carbonic  acid 

gas,  and  the  blood  proceeds  on  its  course,  to  renew  the    / 
cycle  of  its  circulation.  * 

Now,  if  we  study  the  process  of  respiration  and  that  of 
circulation,  with  which  it  is  so  closely  associated,  in  other 
forms  of  life,  we  shall  find  many  differences  in  detail. 
In  the  bird,  for  example,  the  mechanism  of  respiration  is 
different.  There  is  no  diaphragm,  and  the  lungs  are 
scarcely  distensible.  There  are,  however,  large  air-sacs  in 
the  abdomen,  in  the  thoracic  region,  in  the  fork  of  the 
merry-thought,  and  elsewhere.  These  are  distensible,  and 
to  reach  them  the  air  has  to  pass  through  the  lungs,  and 
as  it  thus  passes  through  the  delicate  tubes  of  the  lungs,  it 
supplies  the  blood  with  oxygen  and  takes  away  carbonic 


Fig.  6. — Diagram  of  circu- 
lation. 
L.A.,  left  auricle  of  the  heart; 


24  Animal  Life  and  Intelligence. 

acid  gas.  In  the  frog  there  is  no  diaphragm,  and  there 
are  no  ribs.  The  lungs  are  hollow  sacs  with  honey-combed 
sides,  and  they  are  inflated  from  the  mouth,  which  is 
used  as  a  force-pump  for  this  purpose.  In  the  fish  there 
are  no  lungs,  respiration  being  effected  by  means  of  gills. 
In  these  organs  the  blood  is  separated  from  the  water 
which  passes  over  them  (being  gulped  in  by  the  mouth 
and  forced  out  between  the  gill-covers)  by  only  a  thin 
organic  film,  so  that  it  can  take  up  the  oxygen  dissolved  in 
the  water,  and  give  up  to  the  water  the  carbonic  acid  it 
contains.  In  fishes,  too,  we  have  only  one  receiver  and 
one  force-pump,  the  blood  passing  through  the  gills  on  its 
way  to  the  various  parts  of  the  body.  In  the  lobster,  again, 
there  are  gills,  but  the  mechanism  by  which  the  water  is 
drawn  over  them  is  quite  different,  and  the  blood  passes 
through  them  .on  its  way  to  the  heart,  after  passing 
through  the  various  organs  of  the  body,  not  on  its  way 
from  the  heart,  as  in  vertebrate  fishes.  The  blood,  too, 
has  no  red  blood-discs.  In  the  air-breathing  insects  the 
mechanism  is,  again,  altogether  different.  The  air,  which 
obtains  access  to  the  body  by  spiracles  in  the  sides  (see 
Fig.  1,  p.  3),  is  distributed  by  delicate  and  beautiful  tubes 
to  all  parts  of  the  organs ;  so  that  the  oxygen  is  supplied 
to  the  tissues  directly,  and  not  through  the  intervention  of 
a  blood-stream.  In  the  earthworm,  on  the  other  hand, 
there  is  a  distributing  blood-stream,  but  there  is  no 
mechanism  for  introducing  the  air  within  the  body ;  while 
in  some  of  the  lowliest  forms  of  life  there  is  neither  any 
introduction  of  air  within  the  body  nor  any  distribution 
by  means  of  a  circulating  fluid.  Beginning,  therefore, 
with  the  surface  of  the  body  simply  absorbent  of  oxygen, 
we  have  the  concentration  of  the  absorbent  parts  in  special 
regions,  and  an  increase  in  the  absorbent  surface,  either 
(1)  by  the  pushing  out  of  processes  into  the  surrounding 
medium,  as  in  gills;  or  (2)  by  the  formation  of  internal 
cavities,  tubes,  or  branching  passages,  as  in  lungs  and  the 
tracheal  air-system  of  insects. 

What,  then,  is  the  essential  nature  of  the  respiratory 


The  Process  of  Life.  25 

process  thus  so  differently  manifested  ?  Clearly  the 
supply  of  oxygen  to  the  cellular  tissue-elements,  and, 
generally  closely  associated  with  this,  the  getting  rid  of 
carbonic  acid  gas. 

Jjet  us  now  glance  at  the  life-processes  which  minister 
to  -nutrition,  beginning,  as  before,  with  the  mode  in  which 
these  processes  are  effected  in  ourselves.. 

The  alimentary  canal  is  a  long  tube  running  through 
the  body  from  the  mouth  to  the  vent.  In  the  abdominal 
region  it  is  coiled  upon  itself,  so  that  its  great  length  may 
be  conveniently  packed  away.  Opening  into  this  tube  are 
the  ducts  of  certain  glands,  which  secrete  fluids  which  aid 
in  the  digestion  of  the  food.  Into  the  mouth  there  open 
the  ducts  of  the  salivary  glands,  which  secrete  the  saliva ; 
in  the  stomach  there  are  a  vast  number  of  minute  gastric 
glands ;  in  the  intestine,  besides  some  minute  tubular 
glands,  there  are  the  ducts  of  the  large  liver  (which 
secretes  the  bile)  and  the  pancreas,  or  sweetbread.  Since, 
with  the  exception  of  the  openings  of  these  ducts,  th'e 
alimentary  canal  is  a  closed  tube,  its  contents,  though 
tying  within  the  body,  are  in  a  sense  outside  it,  just  as  the 
fuel  in  a  tubular  boiler,  though  within  the  boiler,  is  really 
outside  it.  The  organic  problem,  therefore,  is  how  to  get 
the  nutritive  materials  through  the  walls  of  the  tube  and 
thus  into  the  body. 

At  an  ordinary  meal  we  are  in  the  habit  of  consuming 
a  certain  amount  of  meat,  with  some  fat,  together  with 
bread  and  potatoes,  and  perhaps  some  peas  or  beans  and 
a  little  salt.  This  is  followed  by,  say,  milky  rice-pudding, 
with  which  we  take  some  sugar;  and  a  cheese  course 
may,  perhaps,  be  added.  The  whole  is  washed  down  with 
water  more  or  less  medicated  with  other  fluid  materials. 
Grouping  these  substances,  there  are  (1)  water  and  salts, 
including  calcium  phosphate  in  the  milk ;  (2)  meat,  peas, 
milk,  and  cheese,  all  of  which  contain  albuminous  or  allied 
materials ;  (3)  bread,  potatoes,  and  rice,  which  contain 
starchy  matters ;  and  here  we  may  place  the  sugar ;  (4) 
fat,  associated  with  the  meat  or  contained  in  the  cream  of 


26  Animal  Life  and  Intelligence. 

the  milk.  Now,  of  all  the  materials  thus  consumed,  only 
the  water,  salts,  and  sugar  are  capable,  in  their  unaltered 
condition,  of  passing  through  the  lining  membrane  of  the 
alimentary  canal,  and  thus  of  entering  the  body.  The 
albuminous  materials,  the  starchy  matter,  and  the  fat — 
that  is  to  say,  the  main  elements  of  the  food — are,  in  their 
raw  state,  absolutely  useless  for  nutritive  purposes. 

The  preparation  of  the  food  begins  in  the  mouth.  The 
saliva  here  acts  upon  some  of  the  starchy  matter,  and 
converts  it  into  a  kind  of  sugar,  which  can  pass  through 
the  lining  membrane  of  the  alimentary  canal,  and  thus 
enter  the  body.  The  fats  and  albuminous  matters  here 
remain  unaltered,  though  they  are  torn  to  pieces  by  the 
mastication  effected  by  the  teeth.  In  the  stomach  the 
albuminous  constituents  of  the  meat  are  attacked  by 
the  gastric  juice  and  converted  into  peptones ;  and  in  this 
new  condition  they,  too,  can  soak  through  the  lining 
membrane  of  the  alimentary  canal,  and  thus  can  enter  the 
body.  In  the  stomach  all  action  on  starch  is  arrested; 
but  in  the  intestine,  through  the  effect  of  a  ferment 
contained  in  the  pancreatic  juice,  this  action  is  resumed, 
and  the  rest  of  the  starch  is  converted  into  absorbable 
sugar.  Another  principle  contained  in  pancreatic  juice 
takes  effect  on  the  albuminous  matters,  and  converts  them 
into  absorbable  peptones.  The  pancreatic  juice  also  acts 
on  the  fats,  converting  them  into  an  emulsion,  that  is  to 
Bay,  causing  them  to  break  up  into  exceedingly  minute 
globules,  like  the  butter  globules  in  milk.  It  furthermore 
contains  a  ferment  which  splits  up  the  fats  into  fatty  acids 
and  glycerine;  and  these  fatty  acids,  with  an  alkaline 
carbonate  contained  in  small  quantities  in  pancreatic  juice, 
form  soluble  soaps,  which  further  aid  in  emulsifying  fats. 
The  bile  also  aids  in  emulsifying  fats. 

The  effect,  then,  of  the  various  digestive  fluids  upon 
the  food  is  to  convert  the  starch,  albuminous  material, 
and  fat  into  sugar,  peptones,  glycerine,  and  soap,  and  thus 
render  them  capable  of  passing  through  the  lining  mem- 
brane of  the  canal  into  the  body. 


The  Process  of  Life.  27 

The  materials  thus  absorbed  are  either  taken  up  into 
the  blood-stream  or  pass  into  a  separate  system  of  vessels 
called  laeteals.  All  the  blood  which  comes  away  from  the 
alimentary  canal  passes  into  the  liver,  and  there  undergoes 
a  good  deal  of  elaboration  in  that  great  chemical  labora- 
tory of  the  body.  The  fluid  in  the  laeteals  passes  through 
lymphatic  glands,  in  which  it  too  undergoes  some  elabora- 
tion before  it  passes  into  the  blood-stream  by  a  large  vessel 
or  duct. 

Thus  the  blood,  which  we  have  seen  to  be  enriched  with 
oxygen  in  the  lungs,  is  also  enriched  with  prepared  nutri- 
tive material  through  the  processes  of  digestion  and  absorp- 
tion in  the  alimentary  organs  and  elaboration  in  the  liver 
and  lymphatic  glands. 

Here  let  us  again  notice  that  the  details  of  the  process 
of  nutrition  vary  very  much  in  different  forms  of  life.  In 
some  mammals  the  organs  of  digestion  are  specially  fitted 
to  deal  with  a  flesh  diet ;  in  others  they  are  suited  for  a 
diet  of  herbs.  In  the  graminivorous  birds  the  grain  is 
swallowed  whole,  and  pounded  up  in  the  gizzard.  The 
leech  swallows  nothing  but  blood.  The  earthworm  pours 
out  a  secretion  on  the  leaves,  by  which  they  are  partially 
digested  before  they  enter  the  body.  Many  parasitic 
organisms  have  no  digestive  canal,  the  nutritive  juices  of 
their  host  being  absorbed  by  the  general  external  surface 
of  the  body.  But  the  essential  life-process  is  in  all  cases 
the  same — the  absorption  of  nutritive  matter  to  be  supplied 
to  the  cell  or  cells  of  which  the  organism  is  built  up. 

Thus  in  the  mammal  the  blood,  enriched  with  oxygen 
in  the  lungs,  and  enriched  also  with  nutritive  fluids,  is 
brought,  in  the  course  of  its  circulation,  into  direct  or 
indirect  contact  with  all  the  myriads  of  living  cells  in  the 
body. 

In  the  first  place,  the  material  thus  supplied  is  utilized 
for  and  ministers  to  the  growth  of  the  organs  and  tissues. 
This  growth  is  effected  by  the  multiplication  of  the  con- 
stituent cells.  The  cells  themselves  have  a  very  limited 
power  of  growth.  But,  especially  in  the  early  stages  of 


28  Animal  Life  and  Intelligence. 

the  life  of  the  organism,  when  well  supplied  with  nutri- 
ment, the  cells  multiply  rapidly,  by  a  process  of  fission, 
or  the  division  of  each  cell  into  two  daughter  cells.  The 
first  part  of  the  cell  to  divide  is  the  nucleus,  the  proto- 
plasmic network  of  which  shows,  during  the  process,  curious 
and  interesting  arrangements  and  groupings  of  the  fibres. 
When  the  nucleus  has  divided,  the  surrounding  protoplasm 
is  constricted,  and  separates  into  two  portions,  each  of 
which  contains  a  daughter  nucleus. 

In  addition  to  the  multiplication  of  cells,  there  is  the 
formation,  especially  during  periods  of  growth,  of  certain 
products  of  cell-life  and  cell-activity.  Bone,  for  example, 
is  a  more  or  less  permanent  product  of  the  activity  of 
certain  specialized  cells. 

There  is,  perhaps,  no  more  wonderful  instance  of  rapid 
and  vigorous  growth  than  the  formation  of  the  antlers  of 
deer.  These  splendid  weapons  and  adornments  are  shed 
and  renewed  every  year.  In  the  spring,  when  they  are 
growing,  they  are  covered  over  with  a  dark  skin  provided 
with  short,  fine,  close-set  hair,  and  technically  termed  "the 
velvet."  If  you  lay  your  hand  on  the  growing  antler,  you 
will  feel  that  it  is  hot  with  the  nutrient  blood  that  is 
coursing  beneath  it.  It  is,  too,  exceedingly  sensitive  and 
tender.  An  army  of  tens  of  thousands  of  busy  living  cells 
is  at  work  beneath  that  velvet  surface,  building  the  bony 
antlers,  preparing  for  the  battles  of  autumn.  Each  minute 
cell  knows  its  work,  and  does  it  for  the  general  good — so 
perfectly  is  the  body  knit  into  an  organic  whole.  It  takes 
up  from  the  nutrient  blood  the  special  materials  it  requires  ; 
out  of  them  it  elaborates  the  crude  bone-stuff,  at  first  soft 
as  wax,  but  ere  long  to  become  as  hard  as  stone ;  and  then, 
having  done  its  work,  having  added  its  special  morsel  to 
the  fabric  of  the  antler,  it  remains  embedded  and  immured, 
buried  beneath  the  bone-products  of  its  successors  or 
descendants.  No  hive  of  bees  is  busier  or  more  replete 
with  active  life  than  the  antler  of  a  stag  as  it  grows 
beneath  the  soft,  warm  velvet.  And  thus  are  built  up  in 
the  course  of  a  few  weeks  those  splendid  "beams,"  with 


The  Process  of  Life.  29 

their  "  tynes "  and  "snags,"  which,  in  the  case  of  the 
wapiti,  even  in  the  confinement  of  our  Zoological  Gardens, 
may  reach  a  weight  of  thirty-two  pounds,  and  which,  in 
the  freedom  of  the  Kocky  Mountains,  may  reach  such  a 
size  that  a  man  may  walk,  without  stooping,  beneath  the 
archway  made  by  setting  up  upon  their  points  the  shed 
antlers.  When  the  antler  has  reached  its  full  size,  a  cir- 
cular ridge  makes  its  appearance  at  a  short  distance  from 
the  base.  This  is  the  "  burr,"  which  divides  the  antler 
into  a  short  "pedicel"  next  the  skull,  and  the  "beam" 
with  its  branches  above.  The  circulation  in  the  blood- 
vessels of  the  beam  now  begins  to  languish,  and  the  velvet 
dies  and  peels  off,  leaving  the  hard,  dead,  bony  substance 
exposed.  Then  is  the  time  for  fighting,  when  the  stags 
challenge  each  other  to  single  combat,  while  the  hinds 
stand  timidly  by.  But  when  the  period  of  battle  is  over, 
and  the  wars  and  loves  of  the  year  are  past,  the  bone 
beneath  the  burr  begins  to  be  eaten  away  and  absorbed, 
through  the  activity  of  certain  large  bone-eating  cells,  and, 
the  base  of  attachment  being  thus  weakened,  the  beautiful 
antlers  are  shed ;  the  scarred  surface  skins  over  and  heals, 
and  only  the  hair-covered  pedicel  of  the  antler  is  left.* 

Not  only  are  there  these  more  or  less  permanent 
products  of  cell-activity  which  are  built  up  into  the 
framework  of  the  body ;  there  are  other  products  of  a 
less  enduring,  -but,  in  the  case  of  some  of  them,  not  less 
useful  character.  The  secretions,  for  example,  which,  as 
we  have  seen,  minister  in  such  an  important  manner  to 
nutrition,  are  of  this  class.  The  salivary  fluids,  the  gastric 
juice,  the  pancreatic  products,  and  the  bile, — all  of  these 
are  products  of  cell-life  and  cell-activity.  And  then  there 
are  certain  products  of  cell-life  which  must  be  cast  out 
from  the  body  as  soon  as  possible.  These  are  got  rid  of 
in  the  excretions,  of  which  the  carbonic  acid  gas  expelled 
in  the  lungs  and  the  waste-products  eliminated  through 
the  kidneys  are  examples.  They  are  the  ultimate  organic 

*  From  a  popular  article  of  the  author's  on  "  Horns  and  Antlers,"  in 
Atalanta. 


3<D  Animal  Life  and  Intelligence. 

products  of   the    combustion    that    takes    place    in    the 
muscular,  nervous,  and  other  tissues. 

The  animal  organism  has  sometimes  been  likened  to 
a  steam-engine,  in  which  the  food  is  the  fuel  which  enters 
into  combustion  with  the  oxygen  taken  in  through  the 
lungs.  It  may  be  worth  while  to  modify  and  modernize 
this  analogy — always  remembering,  however,  that  it  is  an 
analogy,  and  that  it  must  not  be  pushed  too  far. 

In  the  ordinary  steam-engine  the  fuel  is  placed  in  the 
fire-box,  to  which  the  oxygen  of  the  air  gains  access ;  the 
heat  produced  by  the  combustion  converts  the  water  in 
the  boiler  into  steam,  which  is  made  to  act  upon  the 
piston,  and  thus  set  the  machinery  in  motion.  But  there 
is  another  kind  of  engine,  now  extensively  used,  which 
works  on  a  different  principle.  In  the  gas-engine  the  fuel 
is  gaseous,  and  it  can  thus  be  introduced  in  a  state  of 
intimate  mixture  with  the  oxygen  with  which  it  is  to  unite 
in  combustion.  This  is  a  great  advantage.  The  two  can 
unite  rapidly  and  explosively.  In  gunpowder  the  same 
end  is  effected  by  mixing  the  carbon  and  sulphur  with 
nitre,  which  contains  the  oxygen  necessary  for  their  explo- 
sive combustion.  And  this  is  carried  still  further  in  dyna- 
mite and  gun-cotton,  where  the  elements  necessary  for 
explosive  combustion  are  not  merely  mechanically  mixed, 
but  are  chemically  combined  in  a  highly  unstable  com- 
pound. 

But  in  the  gas-engine,  not  only  is  the  fuel  and  the 
oxygen  thus  intimately  mixed,  but  the  controlled  explo- 
sions and  the  resulting  condensation  are  caused  to  act 
directly  on  the  piston,  and  not  through  the  intervention 
of  water  in  a  boiler.  Whereas,  therefore,  in  the  steam- 
engine  the  combustion  is  to  some  extent  external  to  the 
working  of  the  machine,  in  the  gas-engine  it  is  to  a  large 
extent  internal  and  direct. 

Now,  instead  of  likening  the  organism  as  a  whole  to 
a  steam-engine,  it  is  more  satisfactory  to  liken  each  cell 
to  a  gas-engine.  We  have  seen  that  the  cell-substance 
around  the  nucleus  is  composed  of  a  network  of  proto- 


The  Process  of  Life.  31 

plasm,  the  plasmogen,  enclosing  within  its  meshes  a  more 
fluid  material,  the  plasm.  It  is  probable  that  this  more 
fluid  material  is  an  explosive,  elaborated  through  the  vital 
activity  of  the  protoplasmic  network.  During  the  period 
of  repose  which  intervenes  between  periods  of  activity,  the 
protoplasmic  network  is  busy  in  construction,  taking  from 
the  blood-discs  oxygen,  and  from  the  blood-fluid  carbona- 
ceous and  nitrogenous  materials,  and  knitting  these 
together  into  relatively  unstable  explosive  compounds. 
These  explosive  compounds  are  like  the  mixed  air  and  gas 
of  the  gas-engine.  A  rested  muscle  may  be  likened  to  a 
complex  and  well-organized  battery  of  gas-engines.  On 
the  stimulus  supplied  through  a  nerve-channel  a  series  of 
co-ordinated  explosions  takes  place  :  the  gas-engines  are  set 
to  work ;  the  muscular  fibres  contract ;  the  products  of  the 
explosions  (one  of  which  is  carbonic  acid  gas)  are  taken 
up  and  hurried  away  by  the  blood-stream  ;  and  the  proto- 
plasm sets  to  work  to  form  a  fresh  supply  of  explosive 
material.  Long  before  the  invention  of  the  gas-engine,  long 
before  gun-cotton  or  dynamite  were  dreamt  of,  long  before 
some  Chinese  or  other  inventor  first  mixed  the  ingre- 
dients of  gunpowder,  organic  nature  had  utilized  the 
principle  of  controlled  explosions  in  the  protoplasmic  cell. 

Certain  cells  are,  however,  more  delicately  explosive 
than  others.  Those,  for  example,  on  or  near  the  external 
surface  of  the  body — those,  that  is  to  say,  which  constitute 
the  end  organs  of  the  special  senses — contain  explosive 
material  which  may  be  fired  by  a  touch,  a  sound,  an 
odour,  the  contact  with  a  sapid  fluid  or  a  ray  of  light. 
The  effects  of  the  explosions  in  these  delicate  cells,  rein- 
forced in  certain  neighbouring  nerve-knots  (ganglionic 
cells),  are  transmitted  down  the  nerves  as  along  a  fired 
train  of  gunpowder,  and  thus  reach  that  wonderful  aggre- 
gation of  organized  and  co-ordinated  explosive  cells,  the 
brain.  Here  it  is  again  reinforced  and  directed  (who,  at 
present,  can  say  how  ?)  along  fresh  nerve-channels  to 
muscles,  or  glands,  or  other  organized  groups  of  explosives. 
And  in  the  brain,  somehow  associated  with  the  explosion 


32  Animal  Life  and  Intelligence. 

of  its  cells,  consciousness  and  the  mind-element  emerges ; 
of  which  we  need  only  notice  here  that  it  belongs  to  a 
wholly  different. order  of  being  from  the  physical  activities 
and  products  with  which  we  are  at  present  concerned. 

No  analogies  between  mechanical  contrivances  and 
organic  processes  can  be  pushed  very  far.  To  liken  the 
organic  cell  to  a  gas-engine  is  better  than  to  liken  the 
organism  to  a  steam-engine,  because  it  serves  to  indicate 
the  fact  that  the  fuel  does  not  simply  combine  with  the 
oxygen  in  combustion,  but  that  an  unstable  or  explosive 
combination  of  "fuel"  and  oxygen  is  first  formed;  and 
again,  because  the  effect  of  this  is  direct,  and  not  through 
the  intervention  of  any  substance  to  which  the  combustion 
merely  supplies  the  necessary  heat.  But  beyond  the  fact 
that  a  kind  of  explosive  is  formed  which,  like  a  fulminating 
compound,  can  be  fired  by  a  touch,  there  is  no  very  close 
analogy  to  be  drawn.  Nor  must  we  press  the  explosion 
analogy  too  far.  The  essential  thing  would  seem  to  be 
this — which,  perhaps,  the  analogy  may  have  served  to 
lead  up  to — that  the  vital  protoplasmic  network  of  the 
cell  has  the  power  of  building  up  complex  and  unstable 
chemical  compounds,  which  are  probably  stored  in  the 
plasm  within  the  spaces  between  the  threads  of  the  net- 
work; and  that  these  unstable  compounds,  under  the 
influence  of  a  stimulus  (or,  possibly,  sometimes  sponta- 
neously) break  down  into  simpler  and  more  stable  com- 
pounds.*/In  the  case  of  muscle-cells,  this  latter  change 
is  accompanied  by  an  alteration  in  length  of  the  fibres 
and  consequent  movements  in  the  organism,  the  products 
of  the  disruptive  change  being  useless  or  harmful,  and 
being,  therefore,  got  rid  of  as  soon  as  possible.  But  very 

*  It  will  be  well  here  to  introduce  the  technical  terms  for  these  changes. 
The  general  term  for  chemical  actions  occurring  in  the  tissues  of  a  living 
creature  is  metabolism ;  where  the  change  is  of  such  a  nature  that  complex 
and  unstable  compounds  are  built  up  and  stored  for  a  while,  it  is  called 
anabolism ;  where  complex  unstable  compounds  break  up  into  less  complex 
and  relatively  stable  compounds,  the  term  katabolism  is  applied.  "We  shall 
speak  of  anabolic  changes  as  constructive ;  katabolic,  as  disruptive,  or  some- 
times, explosive. 


The  Process  of  Life.  33 

frequently  the  products  of  explosive  activity  are  made  use 
of.  In  the  case  of  bone-cells,  one  of  the  products  of 
disruption  is  of  permanent  use  to  the  organism,  and 
constitutes  the  solid  framework  of  the  skeleton.  In  the 
case  of  the  secreting  cells  of  the  salivary  and  other  diges- 
tive glands,  one  of  the  disruptive  products  is  of  temporary 
value  for  the  preparation  of  the  food.  It  is  exceedingly 
probable  that  these  useful  products  of  disruption,  perma- 
nent or  temporary,  took  their  origin  in  waste  products  for 
which  natural  selection  has  found  a  use,  and  which  have 
been,  through  natural  selection,  rendered  more  and  more 
efficacious.  This,  however,  is  a  question  we  are  not  at 
present  in  a  position  to  discuss. 

In  the  busy  hive  of  cells  which  constitutes  what  we 
call  the  animal  body,  there  is  thus  ceaseless  activity. 
During  periods  of  apparent  rest  the  protogen  filaments 
of  the  cell -net  are  engaged  in  constructive  work,  building 
up  fresh  supplies  of  complex  and  unstable  materials, 
which,  during  periods  of  apparent  activity,  break  up  into 
simpler  and  more  stable  substances,  some  of  which  are 
useful  to  the  organism  while  others  must  be  got  rid 
of  as  soon  as  possibleu  From  another  point  of  view,  the 
cells  during  apparent  rest  are  storing  up  energy  which 
is  utilized  by  the  organism  during  its  periods  of  activity. 
The  storing  up  of  available  energy  may  be  likened  to  the 
winding  up  of  a  watch  or  clock ;  it  is  during  apparent  rest 
that  the  cell  is  winding  itself  up ;  and  thus  we  have  the 
apparent  paradox  that  the  cell  is  most  active  and  doing 
most  work  when  it  is  at  rest.  During  the  repose  of  an 
organ,  in  fact,  the  cells  are  busily  working  in  preparation 
for  the  manifestation  of  energetic  action  that  is  to  follow. 
Just  as  the  brilliant  display  of  intellectual  activity  in  a 
great  orator  is  the  result  of  the  silent  work  of  a  lifetime, 
so  is  the  physical  manifestation  of  muscular  power  the 
result  of  the  silent  preparatory  work  of  the  muscle-cells.* 

One  point  to  be  specially  noted  is  the  varied  activity 

*  I  do  not  mean,  of  course,  to  imply  that  there  is  no  reconstruction  during 
activity,  but  that  it  is  then  distinctly  outbalanced  by  disruptive  changes. 

D 


34  Animal  Life  and  Intelligence. 

of  the  cells.  While  they  are  all  working  for  the  general 
good  of  the  organism,  they  are  divided  into  companies,  each 
with  a  distinct  and  definite  kind  of  work.  This  is  known 
as  the  physiological  division  of  labour.  It  is  accompanied 
by  a  morphological  differentiation  of  structure.  By  the 
form  of  a  cell,  therefore,  we  can  generally  recognize  the 
kind  of  work  it  has  to  perform.  The  unstable  compounds 
produced  by  the  various  cells  must  also  be  different, 
though  not  much  is  known  at  present  on  this  subject. 
The  unstable  compound  which  forms  bone  and  that  which 
forms  the  salivary  ferment,  the  unstable  matter  elaborated 
by  nerve-cells  and  that  built  up  by  muscle-cells,  are  in 
all  probability  different  in  their  chemical  nature.  Whether 
the  formative  plasmogen  from  which  these  different  sub- 
stances originate  is  in  all  cases  the  same  or  in  different 
cases  different,  we  do  not  know. 

It  may,  perhaps,  seem  strange  that  the  products  of 
cellular  life  should  be  reached  by  the  roundabout  process 
of  first  producing  a  very  complex  substance  out  of  which 
is  then  formed  a  less  complex  substance,  useful  for  per- 
manent purposes,  as  in  bone,  or  temporary  purposes,  as 
in  the  digestive  fluids.  It  seems  a  waste  of  power  to  build 
up  substances  unnecessarily  complex  and  stored  with  an 
unnecessarily  abundant  supply  of  energy.  Still,  though 
we  do  not  know  that  this  course  is  adopted  in  all  cases, 
there  is  no  doubt  that  it  is  adopted  in  a  great  number  of 
instances.  And  the  reason  probably  is  that  by  this  method 
the  organs  are  enabled  to  act  under  the  influence  of 
stimuli.  They  are  thus  like  charged  batteries  ready  to 
discharge  under  the  influence  of  the  slightest  organic  touch. 
In  this  way,  too,  is  afforded  a  means  by  which  the  organ 
is  not  dependent  only  upon  the  products  of  the  immediate 
activity  of  the  protoplasm  at  the  time  of  action,  but  can 
utilize  the  store  laid  up  during  a  considerable  preceding 
period. 

Sufficient  has  now  been  said  to  illustrate  the  nature 
of  the  process  of  life.  The  fact  that  I  wish  to  stand  out 
clearly  is  that  the  animal  body  is  stored  with  large 


The  Process  of  Life.  35 

quantities  of  available  energy  resident  in  highly  complex 
and  unstable  chemical  compounds,  elaborated  by  the 
constructive  energy  of  the  formative  protoplasm  of  its 
constituent  cells.  These  unstable  compounds,  eminently 
explosive  according  to  our  analogy,  are  built  up  of  materials 
derived  from  two  different  sources — from  the  nutritive 
matter  (containing  carbon,  hydrogen,  and  nitrogen) 
absorbed  in  the  digestive  organs,  and  from  oxygen  taken 
up  from  the  air  in  the  lungs.  The  cells  thus  become 
charged  with  energy  that  can  be  set  free  on  the  application 
of  the  appropriate  stimulus,  which  may  be  likened  to  the 
spark  that  fires  the  explosive. 

Let  us  note,  in  conclusion,  that  it  is  through  the  blood- 
system,  ramifying  to  all  parts  of  the  body,  and  the  nerve- 
system,  the  ramifications  of  which  are  not  less  perfect, 
that  the  larger  and  higher  organisms  are  knit  together  into 
an  organic  whole.  The  former  carries  to  the  cell  the  raw 
materials  for  the  elaboration  of  its  explosive  products, 
and,  after  the  explosions,  carries  off  the  waste  products 
which  result  therefrom.  The  nerve-fibres  carry  the  stimuli 
by  which  the  explosive  is  fired,  while  the  central  nervous 
system  organizes,  co-ordinates,  and  controls  the  explosions, 
and  directs  the  process  of  reconstruction  of  the  explosive 
compounds. 


36  Animal  Life  and  Intelligence. 


CHAPTER  III. 

REPRODUCTION  AND  DEVELOPMENT. 

WE  have  now  to  turn  to  a  fresh  aspect  of  animal  life, 
that  of  reproduction ;  and  it  will  be  well  to  connect  this 
process  as  closely  as  possible  with  the  process  of  life  in 
general,  of  which  it  is  a  direct  outcome. 

It  will  be  remembered  that,  in  the  last  chapter,  it  was 
shown  that  the  essential  feature  in  the  process  of  life  is 
the  absorption  by  living  protoplasm  of  oxygen  on  the  one 
hand  and  nutritive  matter  on  the  other  hand,  and  the 
kneading  of  these  together,  in  subtle  metabolism,  into 
unstable  compounds,  which  we  likened  to  explosives.  This 
is  the  first,  or  constructive,  stage  of  the  life-process. 
Thereupon  follows  the  second,  or  disruptive,  stage.  The  un- 
stable compounds  break  down  into  more  stable  products, — 
they  explode,  according  to  our  analogy ;  and  accompanying 
the  explosions  are  manifestations  of  motor  activity — of  heat, 
sometimes  of  light  and  electrical  phenomena.  But  in  the 
economy  of  nature  the  products  of  explosion  are  often 
utilized,  and  in  the  division  of  labour  among  cells  the 
explosions  of  some  of  them  are  directed  specially  to  the 
production  of  substances  which  shall  be  of  permanent  or 
temporary  use — for  digestion,  as  in  the  products  of  the 
salivary,  gastric,  and  intestinal  glands ;  for  support,  as  in 
bone,  cartilage,  and  skeletal  tissue  generally ;  or  as  a 
store  of  nutriment,  in  fat  or  yolk.  The  constructive  pro- 
ducts of  protoplasmic  activity  seem  for  the  most  part  to  be 
lodged  in  the  spaces  between  the  network  of  formative 
protoplasm.  The  disruptive  products — those  of  them,  that 
is  to  say,  which  are  of  temporary  or  permanent  value  to 


Reproduction  and  Development.  37 


the  organism — accumulate  either  within  the  cell,  some- 
times at  one  pole,  sometimes  at  the  centre,  as  in  the  case 
of  the  yolk  of  eggs,  or  around  the  cell,  as  in  the  case  of 
cartilage  or  bone. 

Apart  from  and  either  preceding  or  accompanying 
these  phenomena,  is  the  growth  or  increase  of  the  forma- 
tive protoplasm  itself;  concerning  which  the  point  to  be 
here  observed  is  that  it  is  not  indefinite,  but  limited. 
This  was  first  clearly  enunciated  by  Herbert  Spencer,  and 
may  be  called  Spencer's  law.  In  simplest  expression  it 
may  thus  be  stated :  Volume  tends  to  outrun  surface.  Take 
a  cube  measuring  one  inch  in  the  side ;  its  volume  is  one 
cubic  inch,  its  surface  six  square  inches.  Eight  such  cubes 
will  have  a  surface  of  (6  x  8)  forty-eight  square  inches. 
But  let  these  eight  be  built  into  a  larger  cube,  two  inches 
in  the  side,  and  it  will  be  found  that  the  surface  exposed  is 
now  only  twenty-four  square  inches.  While  the  volume 
has  been  increased  eight  times,  the  surface  has  been 
increased  only  four  times.  With  increase  of  size,  volume 
tends  to  outrun  surface.  But  in  the  organic  cell  the 
nutritive  material  and  oxygen  are  absorbed  at  the  surface, 
while  the  explosive  changes  occur  throughout  its  mass. 
Increase  of  size,  therefore,  cannot  be  carried  beyond  certain 
limits,  for  the  relatively  diminished  surface  is  unable  to 
supply  the  relatively  augmented  mass  with  material  for 
elaboration  into  unstable  compounds.  Hence  the  cell 
divides  to  afford  the  same  mass  increased  surface.  This 
process  of  cell-division  is  called  fission,  and  in  some  cases 
cleavage. 

We  will  now  proceed  to  pass  in  review  the  phenomena 
of  reproduction  and  development  in  animals. 

Attention  has  already  been  drawn  to  the  difference 
between  those  lowly  organisms,  each  of  which  is  composed 
of  a  single  cell — the  protozoa,  as  they  are  termed — and 
those  higher  organisms,  called  metazoa,  in  which  there 
are  many  cells  with  varied  functions.  Confining  our 
attention  at  first  to  the  former  group  of  unicellular  animals, 
we  find  considerable  diversities  of  form  and  habit,  from 


Animal  Life  and  Intelligence. 


the  relatively  large,  sluggish,  parasitic  Gregarina,  to  the 
active  slipper-animalcule,  or  Paramcecium,  or  the  beautiful, 
stalked  bell-animalcule,  or  Vorticella  /  and  from  the  small, 
slow-moving  amoeba  to  the  minute,  intensely  active  monad. 
In  many  cases  reproduction  is  by  simple  fission,  as  in  the 
amoeba,  where  the  nucleus  first  undergoes  division;  and 
then  the  whole  organism  splits  into  two  parts,  each  with 
its  own  nucleus.  In  other  cases,  also  numerous,  the 


E-    .^-iPfrT 


A. 

Fig.  7.— Protozoa. 

A,  vorticella  extended.  B,  the  same  contracted.  C,  D,  monads.  E,  amceba.  F,  Para- 
mctcium.  G,  Gregarina.  c.f.,  contractile  fibre ;  c.v.,  contractile  vesicle ;  <i.,disc ;  end.,  endo- 
plast ;  f.v.,  food-vacuole ;  fl.,  flagellum  ;  gu.,  gubernaculum ;  n.,  nucleus ;  p.a.,  potential  anus ; 
p*.,  (in  A)  peristome,  (in  E)  pseudopodium  ;  vt.,  vestibule. 

organism  passes  into  a  quiescent  state,  and  becomes  sur- 
rounded with  a  more  or  less  toughened  cyst.  The  nucleus 
then  disappears,  and  the  contents  of  the  cyst  break  up 
into  a  number  of  small  bodies  or  spores.  Eventually  the 
cyst  bursts,  and  the  spores  swarm  forth.  In  the  case  of 
some  active  protozoa  the  minute  creatures  that  swarm  forth 
are  more  or  less  like  the  parent ;  but  .in  the  more  sluggish 
kinds  the  minute  forms  are  more  active  than  the  parent. 
Thus  in  the  case  of  the  gregarina,  the  minute  spore- 
products  are  like  small  amoebse ;  while  in  other  instances 


Reproduction  and  Development.  39 

the  embryos,  if  so  we  may  call  them,  have  a  whip-like 
cilium  like  the  monads. 

Very  frequently,  however,  there  is,  in  the  protozoa,  a 
further  process,  which  would  seem  to  be  intimately 
associated  with  fission  or  the  formation  of  spores,  as  the 
case  may  be.  This  is  known  as  conjugation.  Among 
monads,  for  example,  two  individuals  may  meet  together, 
conjugate,  and  completely  fuse  the  one  into  the  other.  A 
triangular  cyst  results.  After  a  while,  the  cyst  bursts,  and 
an  apparently  homogeneous  fluid  escapes.  The  highest 
powers  of  the  microscope  fail  to  disclose  in  it  any  germ  of 
life ;  and  there,  at  first  sight,  would  seem  to  be  an  end  of 
the  matter.  But  wait  and  watch ;  and  there  will  appear 
in  the  field  of  the  microscope,  suddenly  and  as  if  by  magic, 
countless  minute  points,  which  prolonged  watching  shows 
to  be  growing.  And  when  they  have  further  grown,  each 
distinct  point  is  seen  to  be  a  monad. 

In  the  slipper-animalcule,  conjugation  is  temporary. 
But  during  the  temporary  fusion  of  the  two  individuals 
important  changes  are  said  to  occur.  In  these  infusorians 
there  is,  beside  the  nucleus,  a  smaller  body,  the  paranu- 
cleus.  This,  in  the  case  of  conjugating  pararnoacia,  appears 
to  divide  into  two  portions,  of  which  one  is  mutually  ex- 
changed. Thus  when  two  slipper-animalcules  are  in  con- 
jugation, the  paranucleus  of  each  breaks  into  two  parts,  a 
and  6,  of  which  a  is  retained  and  b  handed  over  in  exchange. 
The  old  a  and  the  new  b  then  unite,  and  each  paramoecium 
goes  on  its  separate  way.  M.  Maupas,  who  has  lately 
reinvestigated  this  matter,  considers,  as  the  result  of  his 
observations  on  another  infusorian  (Stylonichia) ,  that 
without  conjugation  these  organisms  become  exhausted, 
and  multiplication  by  fission  comes  to  a  standstill.  If  this 
be  so,  conjugation  is,  in  these  organisms,  necessary  for  the 
continuance  of  the  race.  But  Eichard  Hertwig  has  recently 
shown  that  this  is,  at  any  rate,  not  universally  true. 

In  the  bell-animalcule,  fission  takes  place  in  such  a 
manner  as  to  divide  the  bell  into  two  equal  portions. 
Thus  there  are  two  bells  to  one  stalk.  But  the  fate  of  the 


4O  Animal  Life  and  Intelligence. 

two  is  not  the  same.  One  remains  attached  to  the  stalk, 
and  expands  into  a  complete  vorticella.  The  other  remains 
pear-shaped,  and  develops  round  the  posterior  region  of 
the  body  a  girdle  of  powerful  vibratile  cilia,  by  the  lashing 
of  which  the  animalcule  tears  itself  away  from  the  parent 
stem,  and  swims  off  through  the  water.  After  a  short 
active  existence,  it  settles  down  in  a  convenient  spot, 
adhering  by  its  posterior  extremity.  The  hinder  girdle  of 
cilia  is  lost  or  absorbed,  a  stalk  is  rapidly  developed,  and 
the  organism  expands  into  a  perfect  vorticella. 

In  some  cases,  however,  the  fission  is  of  a  different 
character,  with  different  results.  It  may  be  very  unequal, 
so  that  a  minute,  free-swimming  animalcule  is  disengaged ; 
or  minute  animalcules  may  result  by  repetition  of  division. 
In  either  case  the  minute  form  conjugates  with  an  ordinary 
vorticella,  its  smaller  mass  being  completely  merged  in  the 
larger  volume  of  its  mate. 

There  are,  of  course,  many  variations  in  detail  in  the 
modes  of  protozoan  reproduction  ;  but  we  may  say  that, 
omitting  such  details,  reproduction  is  either  by  simple 
fission  or  by  spore-formation;  and  that  these  processes 
are  in  some  cases  associated  with,  and  perhaps  dependent 
on,  the  temporary  or  permanent  union  of  two  individuals 
in  conjugation. 

It  is  essential  to  notice  that  the  results  of  fission  or  of 
spore-formation  separate,  each  going  on  its  own  way.  Hence 
such  development  as  we  find  in  the  protozoa  results  from 
differentiations  within  the  limits  of  the  single  cell.  Thus 
the  bell-animalcule  has  a  well-defined  and  constant  form  ; 
a  definite  arrangement  of  cilia  round  the  rim  and  in  the 
vestibule  by  which  food  finds  entrance  to  the  body.  The 
outer  layer  of  the  body  forms  a  transparent  cuticle,  beneath 
which  is  a  so-called  "myophan  "  layer,  continuous  with  a 
contractile  thread  in  the  stalk.  Within  the  substance  of 
the  body  is  a  pulsating  cavity,  or  contractile  vesicle,  and  a 
nucleus.  Such  is  the  nature  of  the  differentiation  which 
may  go  on  within  the  protozoan  cell. 

When  we  pass  to  the  metazoa,  we  find  that  the  method 


Reproduction  and  Development.  41 


of  differentiation  is  different.  These  organisms  are  com- 
posed of  many  cells ;  and  instead  of  the  parts  of  the  cell 
differentiating  in  several  directions,  the  several  cells  differ- 
entiate each  in  its  own  special  direction.  This  is  known 
as  the  physiological  division  of  labour.  The  cells  merge 
their  individuality  in  the  general  good  of  the  organism. 
Each,  so  to  speak,  cultivates  some  special  protoplasmic 
activity,  and  neglects  everything  else  in  the  attainment  of 
this  end.  The  adult  metazoan,  therefore,  consists  of  a!, 
number  of  cells  which  have  diverged  in  several,  sometimes 
many,  directions. 

In  some  of  the  lower  metazoans,  reproduction  may  be 
effected  by  fission.  Thus  the  fresh-water  hydra  is  said  to 
divide  into  two  parts,  each  of  which  grows  up  into  a  perfect 
hydra.  It  is  very  doubtful,  however,  whether  this  takes 
place  normally  in  natural  life.  But  there  is  no  doubt  that 
if  a  hydra  be  artificially  divided  into  a  number  of  special 
pieces,  each  will  grow  up  into  a  perfect  organism,  so  long 
as  each  piece  has  fair  samples  of  the  different  cells  which 
constitute  the  body-wall.  Sponges  and  sea-anemones  may 
also  be  divided  and  subdivided,  each  part  having  the  power 
of  reproducing  the  parts  that  are  thus  cut  away.  When 
a  worm  is  cut  in  half  by  the  gardener's  spade,  the  head 
end  grows  a  new  tail ;  and  it  is  even  stated  that  a  worm 
not  only  survived  the  removal  of  the  first  five  rings,  in- 
cluding the  brain,  mouth,  and  pharynx,  but  within  fifty- 
eight  days  had  completely  regenerated  these  parts. 

Higher  up  in  the  scale  of  metazoan  life,  animals  have 
the  power  of  regenerating  lost  limbs.  The  lobster  that 
has  lost  a  claw  reproduces  a  new  one  in  its  stead.  A  snail 
will  reproduce  an  amputated  "horn,"  or  tentacle,  many 
times  in  succession,  reproducing  in  each  case  the  eye,  with 
its  lens  and  retina.  Even  a  lizard  will  regenerate  a  lost 
tail  or  a  portion  of  a  leg.  In  higher  forms,  regeneration 
is  restricted  to  the  healing  of  wounds  and  the  mending  of 
broken  bones. 

Closely  connected  with  this  process  of  regeneration  of 
lost  parts  is  the  widely  prevalent  process  of  reproduction 


42  Animal  Life  and  Intelligence. 

by  budding.  The  cut  stump  of  the  amputated  tentacle  of 
the  hydra  or  the  snail  buds  forth  a  new  organ.  But  in  the 
hydra,  during  the  summer  months,  under  normal  circum- 
stances, a  bud  may  make  its  appearance  and  give  rise  to 
a  new  individual,  which  will  become  detached  from  the 
parent,  to  lead  a  separate  existence.  In  other  organisms 
allied  to  the  hydra  the  buds  may  remain  in  attachment, 
and  a  colony  will  result.  This,  too,  is  the  result  of  budding 
in  many  of  the  sponges.  In  some  worms,  too,  budding 
may  occur.  In  the  fresh-water  worm  (Chtetogaster  limncei) 
the  animal,  as  we  ordinarily  see  it,  is  a  train  of  individuals, 
one  budded  off  behind  the  other— the  first  fully  developed, 
those  behind  it  in  various  stages  of  development.  The 
individuals  finally  separate  by  transverse  division.  Another 
more  lowly  worm  (Microstomum  lineare,  a  Turbellarian)  may 
bud  off  in  similar  fashion  a  chain  of  ten  or  fifteen  indi- 
viduals. In  these  cases  budding  is  not  far  removed  from 
fission. 

Now,  in  the  case  of  reproduction  by  budding,  as  in  the 
hydra,  a  new  individual  is  produced  from  some  group  of  cells 
in  the  parent  organism.  From  this  it  is  but  a  step — a  step, 
however,  of  the  utmost  importance — to  the  production  of 
a  new  individual  from  a  single  cell  from  the  tissues  of  the 
parental  organism.  Such  a  reproductive  cell  is  called  an 
egg-cell,  or  ovum.  In  the  great  majority  of  cases,  to  enable 
the  ovum  to  develop  into  a  new  individual,  it  is  necessary 
that  the  egg-cell  should  conjugate  or  fuse  with  a  minute, 
active  sperm-cell,  generally  derived  from  a  different  parent. 
This  process  of  fusion  of  germinal  cells  is  called  fertiliza- 
tion (see  Fig.  5,  p.  13). 

In  sponges,  the  cells  which  become  ova  or  sperms  lie 
scattered  in  the  mid-layer  between  the  ciliated  layers  which 
line  the  cavities  and  spaces  of  the  organism.  Sometimes 
the  individual  sponge  produces  only  ova  ;  sometimes  only 
sperms ;  sometimes  both,  but  at  different  periods.  The 
cells  which  become  ova  increase  in  size,  are  passive,  and 
rich  in  reserve  material  elaborated  by  their  protoplasm. 
The  cells  which  become  sperms  divide  again  and  again, 


Reproduction  and  Development. 


43 


and  thus  produce  minute  active  bodies,  adance  with  rest- 
less motion.     These  opposite  tendencies  are  repeated  and  ] 
emphasized  throughout  the  animal  kingdom — ova  relatively  \ 
large,   passive,   and    accumulative    of    reserve    material;  \ 
sperms  minute,  active,  and  the  result  of  repeated  fission.  \ 
The  active  sperm,  when  it  unites  with  the  ovum,  imports 
into  it  a  tendency  to  fission,  or  cleavage  ;  but  the  resulting 
cells   do  not    part   and   scatter — they  remain   associated 
together,  and  in  mutual  union  give  rise  to  a  new  sponge. 

In  the  hydra,  generally  near  the  foot  or  base  of  attach- 
ment, a  rounded  swelling  often  makes  its  appearance  in 


'     Fig.  8.— Hydra  viridis. 

A,  hydra  half  retracted,  with  a  bud  and  an  ovum  attached  to  the  shrunken  ovary ;  B,  a 
small  hydra  firmly  retracted;  C,  a  hydra  fully  extended.  &.,  bud;  /.,  foot;  h.s.,  hypostome; 
own.,  ovum ;  ovy.,  ovary ;  t.,  tentacles ;  ts.t  testis. 

autumn.  Within  this  swelling  one  central  cell  increases 
enormously  at  the  expense  of  the  others.  It  becomes  an 
ovum.  Eventually  it  bursts  through  the  swelling,  but 
remains  attached  for  a  time.  Earely  in  the  same  hydra, 
more  frequently  in  another,  one  or  two  swellings  may  be 
seen  higher  up,  beneath  the  circle  of  tentacles.  Within 
these,  instead  of  the  single  ovum  may  be  seen  a  swarm  of 
sperms,  minute  and  highly  active.  When  these  are  dis- 
charged, one  may  fuse  with  and  fertilize  an  ovum,  occa- 
sionally in  the  same,  but  more  frequently  in  another 
individual,  with  the  result  that  it  develops  into  a  new 
hydra.  Here  there  are  definite  organs — an  ovary  and  a 


44  Animal  Life  and  Intelligence. 

testis — producing  the  ova  or  the  sperms.  But  they  are 
indefinite  and  not  permanent  in  position. 

In  higher  forms  of  life  the  organs  which  are  set  apart 
for  the  production  of  ova  or  sperms  become  definite  in 
position  and  definite  in  structure.  Occasionally,  as  in  the 
snail,  the  same  organ  produces  both  sperms  and  ova,  but 
then  generally  in  separate  parts  of  its  structure.  The  two 
products  also  ripen  at  different  times.  Not  infrequently, 
as  in  the  earthworm,  each  individual  has  both  testes  and 
ovaries,  and  thus  produces  both  ova  and  sperms,  but  from 
different  organs.  The  ova  of  one  animal  are,  however, 
fertilized  by  sperms  from  another.  But  in  the  higher 
invertebrates  and  vertebrates  there  is  a  sex-differentiation 
among  the  individuals,  the  adult  males  being  possessed  of 
testes  only  and  producing  sperms,  the  adult  females  pos- 
sessed of  ovaries  only  and  producing  ova.  There  are  also, 
in  many  cases,  accessory  structures  for  ensuring  that  the 
ova  shall  be  fertilized  by  sperms,  while  sexual  appetences 
are  developed  to  further  the  same  end.  But  however  the 
matter  may  thus  be  complicated,  the  essential  feature  is 
the  same — the  union  of  a  sluggish,  passive  cell,  more  or 
less  laden  with  nutritive  matter,  with  a  minute  active  cell 
with  an  hereditary  tendency  to  fission.* 

It  is  not,  however,  necessary  in  all  cases  that  fertiliza- 
tion of  the  ovum  should  take  place.  The  plant-lice,  or 
Aphides  of  our  rose  trees,  may  produce  generation  after 

*  Professor  Geddes  and  Mr.  J.  Arthur  Thomson,  in  their  interesting  work 
on  "  The  Evolution  of  Sex,"  regard  the  ovum  in  especial,  and  the  female  in 
general,  as  preponderatingly  anabolic  (s^-e  note,  p.  32) ;  while  the  sperm  in 
especial,  and  the  male  in  genera!,  are  on  their  view  preponderatingly  katabolic. 
Kegarding,  as  I  do,  the  food-yolk  as  a  katubolic  product,  I  cannot  altogether 
follow  them.  Thed;fferentiation  seems  to  me  to  have  taken  place  along  diver- 
gent lines  of  katabolism.  In  the  ovum,  katabolism  has  given  rise  to  storage 
products;  in  the  sperm,  to  motor  activities  associated  with  a  tendency  to 
fission.  The  contrast  is  not  between  anabolic  and  katabolic  tendencies,  but 
between  storage  katabolism  and  motor  katabolism.  Nor  do  I  think  that  "  the 
essentially  katabolic  male-cell  brings  to  the  ovum  a  supply  of  characteristic 
waste  products,  or  katastates,  which  stimulate  the  latter  to  division  "  (I.e.,  p. 
lt;2).  I  believe  that  it  brings  an  inherited  tendency  to  fission,  and  thus 
reiutroduces  into  the  fertilized  ovum  the  teudem-y  which,  as  ovum,  it  had 
renounced  in  favour  of  storage  katabolism. 


Reproduction  and  Development.  45 

generation,  and  their  offspring  in  turn  reproduce  in  like 
manner,  without  any  union  or  fusion  of  ovum  or  sperm. 
The  same  is  true  of  the  little  water-fleas,  or  Daphnids ; 
while  in  some  kinds  of  rotifers  fertilization  is  said  never 
to  occur.  It  is  a  curious  and  interesting  fact,  which  seems 
now  to  be  established  beyond  question,  that  drone  bees  are 
developed  from  unfertilized  ova,  the  fertilized  ova  pro- 
ducing either  queens  or  workers,  according  to  the  nature  of 
the  food  with  which  the  grubs  are  supplied.  Where,  as  in 
the  case  of  aphids  and  daptmids,  fertilization  occasionally 
takes  place,  it  would  seem  that  lowered  temperature  and 
diminished  food -supply  are  the  determining  conditions. 
Fertilization,  therefore,  generally  takes  place  in  the 
autumn  ;  the  fertilized  ovum  living  on  in  a  quiescent  state 
during  the  winter,  and  developing  with  the  warmth  of  the 
succeeding  spring.  In  the  artificial  summer  of  a  green- 
house, reproduction  may  continue  for  three  or  four  years 
without  the  occurrence  of  any  fertilization. 

Mention  may  here  be  made  of  some  peculiarly  modified 
modes  of  reproduction  among  the  metazoa.  The  aurelia 
is  a  well-known  and  tolerably  common  jelly-fish.  These 


Fig.  9.— Aurelia:  Life-cycle. 

a,  embryo ;  b,  Hydra  tuba ;  c,  Hydra  tuba,  with  medusoid  segments ;  d,  medusa  separated 
to  lead  free  existence. 

produce  ova,  which  are  duly  fertilized  by  sperms  from  a 
different  individual.  A  minute,  free- swimming  embryo 
develops  from  the  ovum,  which  settles  down  and  becomes 
a  little  polyp-like  organism,  the  Hydra  tuba.  As  growth 
proceeds,  this  divides  or  segments  into  a  number  of  se- 
parable, but  at  first  connected,  parts.  As  these  attain  their 
full  development,  first  one  and  then  another  is  detached 
from  the  free  end,  floats  off,  and  becomes  a  medusoid 


46  Animal  Life  and  Intelligence. 

aurelia.  Thus  the  fertilized  ovum  of  aurelia  develops,  not 
into  one,  but  into  a  number  of  medusae,*  passing  through 
the  Hydra  tuba  condition  as  an  intermediate  stage. 

Many  of  the  hydroid  zoophytes,  forming  colonies  of 
hydra-like  organisms,  give  rise  in  the  warm  months  to 
medusoid  jelly-fish,  capable  of  producing  ova  and  sperms. 
Fertilization  takes  place;  and  the  fertilized  ova  develop 
into  little  hydras,  which  produce,  by  budding,  new  colonies. 
In  these  new  colonies,  again,  the  parts  which  are  to  become 
ovaries  or  testes  float  off,  and  ripen  their  products  in  free- 
swimming,  medusoid  organisms.  Such  a  rhythm  between 
development  from  ova  and  development  by  budding  is 
spoken  of  as  an  alternation  of  generations. 

The  fresh-water  sponge  (Spongilla}  exhibits  an  analogous 
rhythm.  The  ova  are  fertilized  by  sperms  from  a  different 
short-lived  individual.  They  develop  into  sponges  which 
have  no  power  of  producing  ova  or  sperms.  But  on  the 
approach  of  winter  in  Europe,  and  of  the  dry  season  in 
India,  a  number  of  cells  collect  and  group  themselves  into  a 
so-called  gemmule.  Round  this  is  formed  a  sort  of  crust 
beset  with  spicules,  which,  in  some  cases,  have  the  form  of 
two  toothed  discs  united  by  an  axial  shaft.  When  these 
gemmules  have  thus  been  formed,  the  sponge  dies  ;  but  the 
gemmules  live  on  in  a  quiescent  state  during  the  winter  or 
the  dry  season,  and  with  the  advent  of  spring  develop  into 
sponges,  male  or  female.  These  have  the  power  of  pro- 
ducing sperms  or  ova,  but  no  power  of  producing  gemmules. 
The  power  of  producing  ova,  and  that  of  producing  gem- 
mules,  thus  alternates  in  rhythmic  fashion. 

But  one  more  example  of  these  modified  forms  of 
reproduction  can  here  be  cited  (from  the  author's  text-book 
on  "Animal  Biology").  The  liver-fluke  is  a  parasitic 
organism,  found  in  the  liver  of  sheep.  Here  it  reaches 
sexual  maturity,  each  individual  producing  many  thousands 
of  eggs,  which  pass  with  the  bile  into  the  alimentary  canal 
of  the  host,  and  are  distributed  over  the  fields  with  the 

*  On  the  other  hand,  three  ova  of  the  crustacean  Apris  are  said  to  coalesce 
to  form  the  single  ovum  from  which  one  embryo  develops. 


Reproduction  and  Development. 


47 


excreta.  Here,  in  damp  places,  pools,  and  ditches,  free 
and  active  embryos  are  hatched  .out  of  the  eggs.  Each 
embryo  (Fig.  10,  C.,  much  enlarged)  is  covered  with  cilia, 
except  at  the  anterior  end,  which  is  provided  with  a  head- 


-p.s. 


Fig.  10. — Liver-fluke  :  Embryonic  stages.     (After  A.  P.  Thomas.) 

A.  Ovum:  em.,  embryo;  op.,  operculum.  B.  Limnaus  truncatulus  (natural  size).  C.  Free 
embryo:  e.s.,  eye-spot;  ex.,  excretory  vessel;  g.c.,  germinal  cells;  h.p.,  head-papilla.  D. 
Embryo  preparing  to  become  a  sporocyst :  g.c.,  germinal  cells.  K.  Sporocyst :  g.,  gastrtila  ; 
TO.,  morula;  re..,  redia.  F.  Redia:  b.o.,  birth-opening;  ce.,  cercaria;  col.,  collar;  di.,  digestive 
sac;  ph..,  pharynx;  p.pr.,  posterior  processes;  re.,  daughter  redia.  G.  Cercaria:  cys.,  cysto- 
genous  organ  ;  di.,  digestive  sac ;  o.s.,  oral  sucker ;  p.s.,  posterior  sucker ;  ph.,  pharynx. 

papilla  (h.p.}.     When  the  embryo  comes  in  contact  with 
any  object,  it,  as  a  rule,  pauses  for  a  moment,  and  then 


48  Animal  Life  and  Intelligence. 

darts  off  again.  But  if  that  object  be  the  minute  water- 
snail,  Limneeus  truncatulus  (Fig.  10,  B.,  natural  size),  instead 
of  darting  off,  the  embryo  bores  its  way  into  the  tissues 
until  it  reaches  the  pulmonary  chamber,  or  more  rarely 
the  body-cavity.  Here  its  activity  ceases.  It  passes  into 
a  quiescent  state,  and  is  now  known  as  a  sporocyst  (Fig.  10, 
E.).  The  active  embryo  has  degenerated  into  a  mere 
brood-sac,  in  which  the  next  generation  is  to  be  produced. 
For  within  the  sporocyst  special  cells  undergo  division,  and 
become  converted  into  embryos  of  a  new  type,  which  are 
known  as  redia  (F.),  and  which,  so  soon  as  they  are  suffi- 
ciently developed,  break  through  the  wall  of  the  sporocyst. 
They  then  increase  rapidly  in  size,  and  browse  on  the 
digestive  gland  of  the  water-snail  (known  as  the  intermediate 
host),  to  which  congenial  spot  they  have  in  the  mean  time 
migrated.  The  series  of  developmental  changes  is  even 
yet  not  complete.  For  within  the  redise  (besides,  at  times, 
daughter  rediae)  embryos  of  yet  another  type  are  produced 
by  a  process  of  cell-division.  These  are  known  as  cercariee 
(Fig.  10,  G.).  Each  has  a  long  tail,  by  means  of  which 
it  can  swim  freely  in  water.  It  leaves  the  intermediate 
host,  and,  after  leading  a  short,  active  life,  becomes  encysted 
on  blades  of  grass.  The  cyst  is  formed  by  a  special  larval 
organ,  and  is  glistening  snowy  white.  Within  the  cyst  lies 
the  transparent  embryonic  liver-fluke,  which  has  lost  its 
tail  in  the  process  of  encystment. 

The  last  chapter  in  this  life-history  is  that  in  which  the 
sheep  crops  the  blade  of  grass  on  which  the  parasite  lies 
encysted ;  whereupon  the  cyst  is  dissolved  in  the  stomach 
of  the  host,  the  little  liver-fluke  becomes  active,  passes 
through  the  bile-duct  into  the  liver  of  the  sheep,  and  there, 
growing  rapidly,  reaches  sexual  maturity,  and  lays  its 
thousands  of  eggs,  from  each  of  which  a -fresh  cycle  may 
take  its  origin.  The  sequence  of  phenomena  is  charac- 
terized by  discontinuity  of  development.  Instead  of  the 
embryo  growing  up  continuously  into  the  adult,  with  only 
the  atrophy  of  provisional  organs  (e.g.  the  gills  and  tail  of 
the  tadpole,  or  embryo  frog),  it  produces  germs  from  which 


Reproduction  and  Development.  49 

the  adult  is  developed.  Not  merely  provisional  organs,  but 
provisional  organisms,  undergo  atrophy.  In  the  case  of 
the  liver-fluke  there  are  two  such  provisional  organisms, 
the  embryo  sporocyst  and  the  redia. 

We  may  summarize  the  life-cycle  thus — 

1.  Ovum  laid  in  liver  of  sheep,  passes  with  bile   into 
intestine,  and  thence  out  with  the  excreta. 

2.  Free   ciliated   embryo,  in  water   or   on  damp  earth, 
passes  into  pulmonary  cavity  of  lAmneeus  truncatulus,  and 
develops  into 

3.  Sporocyst,  in  which  secondary  embryos  are  developed, 
known  as 

4.  Redice,   which   pass   into   the   digestive   glands   of 
Limnceus,  and  within  which,  besides  daughter  redise,  there 
are  developed  tertiary  embryos,  or 

5.  Cercaria,  which  pass  out  of  the  intermediate  host 
and  become 

6.  Encysted  on  blades  of  grass,  which  are  eaten  by 
sheep.     The  cyst  dissolves,  and  the  young  flukes  pass  into 
the  liver  of  their  host,  each  developing  into 

7.  A  liver-fluke,  sexual,  but  hermaphrodite. 

Here,  again,  we  notice  that  one  fertilized  ovum  gives 
rise  to  not  one,  but  a  number  of  liver-flukes. 

We  must  now  pass  on  to  consider  the  growth  and 
development  of  organisms.  Simple  growth  results  from  the 
multiplication  of  similar  cells.  As  the  child,  for  example, 
grows,  the  framework  of  the  body  and  the  several  organs 
increase  in  size  by  continuous  cell-multiplication.  Develop- 
ment is  differential  growth  ;  and  this  may  be  seen  either  in 
the  organs  or  parts  of  an  organism  or  in  the  cells  themselves. 
As  the  child  grows  up  into  a  man,  there  is  a  progressive 
change  in  his  relative  proportions.  The  head  becomes 
relatively  smaller,  the  hind  limbs  relatively  longer,  and 
there  are  changes  in  the  proportional  size  of  other  organs. 

In  the  development  of  the  embryo  from  the  ovum,  the 
differentiation  is  of  a  deeper  and  more  fundamental 
character.  Cells  at  first  similar  become  progressively 
dissimilar,  and  out  of  a  primitively  homogeneous  mass  of 

E 


50  Animal  Life  and  Intelligence. 

cells  is  developed  a  heterogeneous  system  of  different  but 
mutually  related  tissues. 

This  view  of  development  is,  however,  the  outcome  of 
comparatively  modern  investigation  and  perfected  micro- 
scopical appliances.  The  older  view  was  that  development 
in  all  cases  is  nothing  more  than  differential  growth,  that 
there  is  no  differentiation  of  primitively  similar  into 
ultimately  different  parts.  Within  the  fertilized  ovum  of 
the  horse  or  bird  lay,  it  was  supposed,  in  all  perfection  of 
structure,  a  miniature  racer  or  chick,  the  parts  all  there, 
but  too  minute  to  be  visible.  All  that  was  required  was 
that  each  part  should  grow  in  due  proportion.  Those  who 
held  this  view,  however,  divided  into  two  schools.  The 
one  believed  that  the  miniature  organism  was  contained 
within  the  ovum,  the  function  of  the  sperm  being  merely 
to  stimulate  its  subsequent  developmental  growth.  The 
other  held  'that  the  sperm  was  the  miniature  organism,  the 
ovum  merely  affording  the  food-material  necessary  for  its 
developmental  growth.  In  either  case,  this  unfolding  of 
the  invisible  organic  bud  was  the  evolution  of  the  older 
writers  on  organic  life.  More  than  this.  As  Messrs. 
Geddes  and  Thomson  remind  us,*  "the  germ  was  more 
than  a  marvellous  bud-like  miniature  of  the  adult.  It 
necessarily  included,  in  its  turn,  the  next  generation,  and 
this  the  next — in  short,  all  future  generations.  Germ 
within  germ,  in  ever  smaller  miniature,  after  the  fashion 
of  an  infinite  juggler's  box,  was  the  corollary  logically 
appended  to  this  theory  of  preformation  and  unfolding." 

Modern  embryology  has  completely  negatived  any  such 
view  as  that  of  preformation,  and  as  completely  established 
that  the  evolution  is  not  the  unfolding  of  a  miniature  germ, 
but  the  growth  and  differentiation  of  primitively  similar 
cell-elements.  In  different  animals,  as  might  be  expected, 
the  manner  and  course  of  development  are  different.  We 
may  here  illustrate  it  by  a  very  generalized  and  so  to 
speak  diagrammatic  description  of  the  development  of  a 
primitive  vertebrate. 

*  "  The  Evolution  of  Sex,"  p.  84. 


Reproduction  and  Development. 


The  ovum  before  fertilization  is  a  simple  spherical  cell, 
without  any  large  amount  of  nutritive  material  in  the 
form  of  food-yolk  (A.}.  It  contains  a  nucleus.  Previous 
to  fertilization,  however,  in  many  forms  of  life,  portions  of 
the  nucleus,  amounting  to  three  parts  of  its  mass,  are  got 
rid  of  in  little  "  polar  cells  "  budded  off  from  the  ovum. 
The  import  of  this  process  we  shall  have  to  consider  in 
connection  with  the  subject  of  heredity.  The  sperm  is  also 


Fig.  11. — Diagram  of  development. 
See  text.    The  fine  line  across  G.  indicates  the  plane  of  section  shown  in  S. 

a  nucleated  cell ;  and  on  its  entrance  into  the  ovum  there 
are  for  a  short  time  two  nuclei — the  female  nucleus  proper 
to  the  ovum,  and  the  male  nucleus  introduced  by  the  sperm. 
These  two  unite  and  fuse  to  form  a  joint  nucleus.  Thus  the 
fertilized  ovum  starts  with  a  perfect  blending  of  the  nuclear 
elements  from  two  cells  produced  by  different  parents. 


52  Animal  Life  and  Intelligence. 

Then  sets  in  what  is  known  as  the  segmentation  or 
cleavage  of  the  ovum.  First  the  nucleus  and  then  the  cell 
itself  divides  into  two  equal  halves  (B.),  each  of  these 
shortly  afterwards  again  dividing  into  two.  We  may  call 
the  points  of  intersection  of  these  two  planes  of  division  the 
"  poles,"  and  the  planes  "  vertical  planes."  We  thus  have 
four  cells  produced  by  two  vertical  planes  (C.).  The  next 
plane  of  division  is  equatorial,  midway  between  the  poles. 
By  this  plane  the  four  cells  are  subdivided  into  eight  (D.). 
Then  follow  two  more  vertical  planes  intermediate  between 
the  first  two.  By  them  the  eight  cells  are  divided  into 
sixteen.  These  are  succeeded  by  two  more  horizontal 
planes  midway  between  the  equator  and  the  poles.  Thus 
we  get  thirty-two  cells.  So  the  process  continues  until,  by 
fresh  vertical  and  horizontal  planes  of  division,  the  ovum  is 
divided  into  a  great  number  of  cells. 

But  meanwhile  a  cavity  has  formed  in  the  midst  of  the 
ovum.  This  makes  its  appearance  at  about  the  eight-cell 
stage,  the  eight  cells  not  quite  meeting  in  the  centre  of  the 
ovum.  The  central  cavity  so  formed  is  thus  surrounded 
by  a  single  layer  of  cells,  and  it  remains  as  a  single  layer 
throughout  the  process  of  segmentation,  so  that  there 
results  a  hollow  vesicle  composed  of  a  membrane  constituted 
by  a  single  layer  of  cells  (E.). 

The  cells  on  one  side  of  the  vesicle  are  rather  larger 
than  the  others,  and  the  next  step  in  the  process  is  the 
apparent  pushing  in  of  this  part  of  the  hollow  sphere ;  just 
as  one  might  take  a  hollow  squash  indiarubber  ball,  and 
push  in  one  side  so  as  to  form  a  hollow,  two-layered  cup  (F.). 
The  vesicle,  then,  is  converted  into  a  cup,  the  mouth  of 
which  gradually  closes  in  and  becomes  smaller,  while  the 
cup  itself  elongates  (G.).*  Thus  a  hollow,  two-layered, 
stumpy,  worm-like  embryo  is  produced,  the  outer  layer  of 

*  In  some  forms  of  life  the  opening  of  the  cup  marks  the  position  of  the 
future  mouth  ;  in  others,  of  the  future  vent.  In  yet  others  it  elongates  into 
a  slit,  occupying  the  whole  length  of  the  embryo;  the  middle  part  of  the  slit 
closes  up,  and  the  opening  at  the  far  ends  mark  the  position,  the  one  of  the 
future  mouth,  the  other  of  the  future  vent. 


Reproduction  and  Development.  53 

which  may  be  ciliated,  so  that  by  the  lashing  of  these 
cilia  it  is  enabled  to  swim  freely  in  the  water.  The  inner 
cavity  is  the  primitive  digestive  cavity. 

A  cross- section  through  the  middle  of  the  embryo  at 
this  stage  will  show  this  central  cavity  surrounded  by  a  two- 
layered  body- wall  (H.).  A  little  later  the  following  changes 
take  place  (J.  K.) :  Along  a  definite  line  on  the  surface  of 
the  embryo,  marking  the  region  of  the  back,  the  outer  layer 
becomes  thickened ;  the  edges  of  the  thickened  band  so 
produced  rise  up  on  either  side,  so  as  to  give  rise  to  a 
median  groove  between  them ;  and  then,  overarching  and 
closing  over  the  groove,  convert  it  into  a  tube.  This  tube 
is  called  the  neural  tube,  because  it  gives  rise  to  the 
central  nervous  system.  In  the  region  of  the  head  it 
expands ;  and  from  its  walls,  by  the  growth  and  differentia- 
tion of  the  cells,  there  is  formed — in  the  region  of  the  head, 
the  brain,  and  along  the  back,  the  spinal  cord.  Imme- 
diately beneath  it  there  is  formed  a  rod  of  cells,  derived 
from  the  inner  layer.  This  rod,  which  is  called  the  noto- 
chord,  is  the  primitive  axial  support  of  the  body.  Around 
it  eventually  is  formed  the  vertebral  column,  the  arches 
of  the  vertebrae  embracing  and  protecting  the  spinal  cord. 

Meanwhile  there  has  appeared  between  the  two  primitive 
body-layers  a  third  or  middle  layer.*  The  cells  of  which 
it  is  composed  arise  from  the  inner  layer,  or  from  the  lips 
of  the  primitive  cup  when  the  outer  and  inner  layer  pass 
the  one  into  the  other.  This  middle  layer  at  first  forms 
a  more  or  less  continuous  sheet  of  cells  between  the  inner 
and  the  outer  layers.  But  ere  long  it  splits  into  two 
sheets,  of  which  one  remains  adherent  to  the  inner  layer 
and  one  to  the  outer  layer.  The  former  becomes  the 
muscular  part  of  the  intestinal  or  digestive  tube,  the  latter 
the  lining  of  the  body-wall.  The  space  between  the  two  is 
known  as  the  body-cavity.  Beneath  the  throat  the  heart 
is  fashioned  out  of  this  middle  layer. 

Very  frequently — that  is  to  say,  in  many  animals — the 

*  In  technical  language,  the  outer  layer  of  cells  is  called  the  epiblast,  the 
inner  layer  the  hypoblast,  and  the  mid-layer  between  them  the  mesoblast. 


54  Animal  Life  and  Intelligence. 

opening  by  which  the  primitive  digestive  tube  communi- 
cated with  the  exterior  has  during  these  changes  closed 
up,  so  that  the  digestive  cavity  does  not  any  longer 
communicate  in  any  way  with  the  exterior.  This  is 
remedied  by  the  formation  of  a  special  depression  or  pit 
at  the  front  end  for  the  mouth,  and  a  similar  pit  at  the 
hinder  end.*  These  pits  then  open  into  the  canal,  and 
communications  with  the  exterior  are  thus  established. 
The  lungs  and  liver  are  formed  as  special  outgrowths  from 
the  digestive  tube.  The  ovaries  or  testes  make  their 
appearance  at  a  very  early  period  as  ridges  of  the  middle 
layer  projecting  into  the  body-cavity.  For  some  time  it 
is  impossible  to  say  whether  they  will  produce  sperms  or 
ova ;  and  it  is  said  that  in  many  cases  they  pass  through 
a  stage  in  which  one  portion  has  the  special  sperm-pro- 
ducing, and  another  the  special  ovum-producing,  structure. 
But  eventually  one  or  other  prevails,  and  the  organs 
become  either  ovaries  or  testes. 

Thus  from  the  outer  layer  of  the  primitive  embryo  is 
produced  the  outer  skin,  together  with  the  hairs,  scales, 
or  feathers  which  it  carries ;  from  it  also  is  produced  the 
nervous  system,  and  the  end-organs  of  the  special  senses. 
From  the  inner  layer  is  formed  the  digestive  lining  of  the 
alimentary  tube  and  the  glands  connected  therewith ;  from 
it  also  the  primitive  axial  support  of  the  body.  But  this 
primitive  support  gives  place  to  the  vertebral  column 
formed  round  the  notochord;  and  this  is  of  mid-layer 
origin.  Out  of  the  middle  layer  are  fashioned  the  muscles 
and  framework  of  the  body ;  out  of  it,  too,  the  heart  and 
reproductive  organs.  The  tissues  of  many  of  the  organs 
are  cunningly  woven  out  of  cells  from  all  three  layers. 
The  lens  of  the  eye,  for  example,  is  a  little  piece  of  the 
outer  layer  pinched  off  and  rendered  transparent.  The' 
retina  of  that  organ  is  an  outgrowth  from  the  brain,  which, 

*  In  technical  language,  the  opening  by  which  the  primitive  digestive 
cavity  (or  mesenterori)  communicates  with  the  exterior  is  called  the  blastopore. 
When  this  closes,  the  new  opening  for  the  mouth  is  called  the  stomodceum; 
that  for  the  vent,  the  proctodceum. 


Reproduction  and  Development.  55 

as  we  have  seen,  was  itself  developed  from  the  outer  layer. 
But  round  the  retina  and  the  lens  there  is  woven  from  the 
middle  layer  the  tough  capsule  of  the  eye  and  the  circular 
curtain  or  iris.  The  lining  cells  of  the  digestive  tube  are 
cells  of  the  inner  layer,  but  the  muscular  and  elastic  coats 
are  of  middle-layer  origin.  The  lining  cells  of  the  salivary 
glands  arise  from  the  outer  layer  where  it  is  pushed  in  to 
form  the  mouth-pit ;  but  the  supporting  framework  of  the 
glands  is  derived  from  the  cells  of  the  middle  layer. 

Enough  has  now  been  said  to  give  some  idea  of  the 
manner  in  which  the  different  tissues  and  organs  of  the 
organism  are  elaborated  by  the  gradual  differentiation  of 
the  initially  homogeneous  ovum.  The  cells  into  which  the 
fertilized  egg  segments  are  at  first  all  alike;  then  comes  the 
divergence  between  those  which  are  pushed  in  to  line  the 
hollow  of  the  cup,  and  those  which  form  its  outer  layer. 
Thereafter  follows  the  differentiation  of  a  special  band  of 
outer  cells  to  form  the  nervous  system,  and  a  special  rod, 
derived  from  the  inner  cells,  to  form  the  primitive  axial 
support.  And  when  the  middle  layer  has  come  into  exist- 
ence, its  cells  group  themselves  and  differentiate  along 
special  lines  to  form  gristle  or  bone,  blood  or  muscle. 

The  description  above  given  is  a  very  generalized  and 
diagrammatic  description.  There  are  various  ways  in 
which  complexity  is  introduced  into  the  developmental 
process.  The  store  of  nutritive  material  present  in  the 
egg,  for  example,  profoundly  modifies  the  segmentation 
so  that  where,  as  in  the  case  of  birds'  eggs,  there  is  a  large 
amount  of  food-yolk,  not  all  the  ovum,  but  only  a  little 
patch  on  its  surface,  undergoes  segmentation.  In  this  little 
patch  the  embryo  is  formed.  Break  open  an  egg  upon 
which  a  hen  has  been  sitting  for  five  or  six  days,  and  you 
'will  see  the  little  embryo  chick  lying  on  the  surface  of  the 
yolk.  The  large  mass  of  yolk  to  which  it  is  attached  is 
simply  a  store  of  food-material  from  which  the  growing 
ohick  may  draw  its  supplies. 

For  it  is  clear  that  the  growing  and  developing  embryo 
must  obtain,  in  some  way  and  from  some  source,  the  food- 


56  Animal  Life  and  Intelligence. 

stuff  for  its  nutrition.  And  this  is  effected,  among  different 
animals,  in  one  of  three  ways.  Either  the  embryo  becomes 
at  a  very  early  stage  a  little,  active,  voracious,  free- 
swimming  larva,  obtaining  for  itself  in  these  early  days  of 
life  its  own  living ;  as  is  the  case,  for  example,  with  the 
oyster  or  the  star-fish.  Or  the  egg  from  which  it  is  de- 
veloped contains  a  large  store  of  food-yolk,  on  which  it  can 
draw  without  stint ;  as  is  the  case  with  birds.  Or  else  the 
embryo  becomes  attached  to  the  maternal  organism  in 
such  a  way  that  it  can  draw  on  her  for  all  the  nutriment 
which  it  may  require;  as  is  the  case  with  the  higher 
mammals. 

In  both  these  latter  cases  the  food-material  is  drawn 
from  the  maternal  organism,  and  is  the  result  of  parental 
sacrifice;  but  in  different  ways.  In  the  case  of  the^bird, 
the  protoplasm  of  the  ovum  has  acquired  the  'power  of 
storing  up  the  by-products  of  its  vital  activity.  The  ovum 
of  such  an  animal  seems  at  first  sight  a  standing  contra- 
diction to  the  statement,  made  some  pages  back,  that  the 
cell  cannot  grow  to  any  great  extent  without  undergoing 
division  or  fission ;  and  this  because  volume  tends  to  outrun 
surface.  For  the  £olk_of  a  bird's  egg  is  a  single  cell,  and 
is  often  of  large  size.  But  when  we  come  to  examine  care- 
fully these  exceptional  cases  of  very  large  cells — for  what 
we  call  the  yolk  of  an  egg  is,  I  repeat,  composed  of  a  single 
cell — we  find  that  the  formative  protoplasm  is  arranged  as 
a  thin  patch  on  one  side  of  the  yolk  in  the  case  of  the 
bird's  egg,  or  as  a  thin  pellicle  surrounding  the  yolk  in  the 
case  of  that  of  the  lobster  or  the  insect.  All  the  rest  is  a 
product  of  protoplasmic  life  stowed  away  beneath  the  patch 
or  within  the  pellicle.  And  this  stored  material  is  relatively 
stable  and  inert,  not  undergoing  those  vital  disruptive 
changes  which  are  characteristic  of  living  formative  proto- 
plasm. The  mass  of  formative  protoplasm,  even  in  the 
large  eggs  of  birds,  is  not  very  great,  and  is  so  arranged 
as  to  offer  a  relatively  extensive  surface.  All  the  rest,  the 
main  mass  of  the  visible  egg-yolk,  is  the  stored  product  of 
a  specialized  activity  of  the  formative  protoplasm.  But  all 


Reproduction  and  Development.  57 

this  material  is  of  parental  origin — is  elaborated  from  the 
nutriment  absorbed  and  digested  by  the  mother. 

Thus  we  see,  in  the  higher  types  of  life,  parental  sacrifice, 
fosterage,  and  protection.  For  in  the  case  of  mammals 
and  many  birds,  especially  those  which  are  born  in  a 
callow,  half-fledged  condition,  even  when  the  connection  of 
mother  and  offspring  is  severed,  or  the  supplies  of  food-yolk 
are  exhausted,  and  the  young  are  born  or  hatched,  there  is 
still  a  more  or  less  prolonged  period  during  which  the 
weakly  offspring  are  nourished  by  milk,  by  a  secretion  from 
the  crop  ("pigeon's  milk"),  or  by  food-stuff  brought  with 
assiduous  care  by  the  parents.  There  is  a  longer  or 
shorter  period  of  fosterage  and  protection — longer  in  the 
case  of  man  than  in  that  of  any  of  the  lower  animals — ere 
the  offspring  are  fitted  to  fend  for  themselves  in  life's 
struggle. 

And  accompanying  this  parental  sacrifice,  first  in 
supplying  food  for  embryonic'  development,  and  then  in 
affording  fosterage  and  protection  during  the  early  stages 
of  growth,  there  is,  as  might  well  be  supposed,  a  reduction 
in  the  number  of  ova  produced  and  of  young  brought  forth 
or  hatched.  Many  of  the  lower  organisms  lay  hundreds  of 
thousands  of  eggs,  each  of  which  produces  a  living  active 
embryo.  The  condor  has  but  two  downy  fledglings  in  a 
year;  the  gannet  lays  annually  but  a  single  egg;  while 
the  elephant,  in  the  hundred  years  of  its  life,  brings  forth 
but  half  a  dozen  young. 

We  shall  have  to  consider  by  what  means  these  opposite 
tendencies  (a  'tendency  to  produce  enormous  numbers  of 
tender,  ill-equipped  embryos,  and  a  tendency  to  produce 
few  well-equipped  offspring)  have  been  emphasized.  The 
point  now  to  be  noted  is  that  every  organism,  even  the 
slowest  breeder  that  exists,  produces  more  young  than  are 
sufficient  to  keep  up  the  numbers  of  the  species.  If  every 
pair  of  organisms  gave  birth  to  a  similar  pair,  and  if  this 
pair  survived  to  do  likewise,  the  number  of  individuals  in 
the  species  would  have  no  tendency  either  to  increase  or 
to  diminish.  But,  as  a  matter  of  fact,  animals  actually  do 


58  Animal  Life  and  Intelligence. 

produce  from  three  or  four  times  to  hundreds  or  even 
thousands  of  times  as  many  new  individuals  as  are  neces- 
sary in  this  way  to  keep  the  numbers  constant.  This  is 
the  law  of  increase.  It  may  be  thus  stated  :  The  number  of 
individuals  in  every  race  or  species  of  animals  is  tending  to 
increase.  Practically  this  is  only  a  tendency.  By  war,  by 
struggle,  by  competition,  by  the  preying  of  animals  upon 
each  other,  by  the  stress  of  external  circumstances,  the 
numbers  are  thinned  down,  so  that,  though  the  births  are 
many,  the  deaths  are  many  also,  and  the  survivals  few. 
In  the  case  of  those  species  the  numbers  of  which  are 
remaining  constant,  out  of  the  total  number  born  only  two 
survive  to  procreate  their  kind.  We  may  judge,  then,  of 
the  amount  of  extermination  that  goes  on  among  those 
animals  which  produce  embryos  by  the  thousand  or  even 
the  hundred  thousand.  The  effects  of  this  enormous  death- 
rate  on  the  progress  of  the  race  or  species  we  shall  have 
to'  consider  in  the  next  chapter,  when  the  question  of  the 
differentiation  of  species  is  before  us. 

There  is  one  form  of  differentiation,  however,  which  we 
may  glance  at  before  closing  this  chapter — the  differentia- 
tion of  sex.  We  are  not  in  a  position  to  discuss  the  ultimate 
causes  of  sex-differentiation,  but  we  may  here  note  the 
proximate  causes  as  they  seem  to  be  indicated  in  certain 
cases. 

Among  honey-bees  there  are  males  (drones),  fertile 
females  (queens),  and  imperfect  or  infertile  females  (workers). 
It  has  now  been  shown,  beyond  question,  that  the  eggs 
from  which  drones  develop  are  not  fertilized.  The  presence 
or  absence  of  fertilization  in  this  case  determines  the  sex. 
During  the  nuptial  flight,  a  special  reservoir,  possessed  by 
the  queen  bee,  is  stored  with  sperms  in  sufficient  number 
to  last  her  egg-laying  life.  It  is  in  her  power  either  to 
fertilize  the  eggs  as  they  are  laid  or  to  withhold  fertiliza- 
tion. If  the  nuptial  flight  is  prevented,  and  the  reservoir 
is  never  stored  with  sperms,  she  is  incapable  of  laying 
anything  but  drone  eggs.  The  cells  in  which  drones  are 
developed  are  somewhat  smaller  than  those  for  ordinary 


Reproduction  and  Development.  59 

workers ;  but  what  may  be  the  nature  of  the  stimulus  that 
prompts  the  queen  to  withhold  fertilization  we  at  present  do 
not  know.  The  difference  between  the  fertile  queen  and 
the  unfertile  worker  seems  to  be  entirely  a  matter  of 
nutrition.  If  all  the  queen-embryos  should  die,  the 
workers  will  tear  down  the  partitions  so  as  to  throw  three 
ordinary  worker-cells  into  one  ;  they  will  destroy  two  of  the 
embryos,  and  will  feed  the  third  on  highly  nutritious  and 
stimulating  diet ;  with  the  result  that  the  ovaries  and 
accessory  parts  are  fully  developed,  and  the  grub  that 
would  have  become  an  infertile  worker  becomes  a  fertile 
queen.  And  one  of  the  most  interesting  points  about  this 
change,  thus  wrought  by  a  stimulating  diet,  is  that  not 
only  are  the  reproductive  powers  thus  stimulated,  but  the 
whole  organism  is  modified.  Size,  general  structure,  sense- 
organs,  habits,  instincts,  and  character  are  all  changed 
with  the  development  of  the  power  of  laying  eggs.  The 
organism  is  a  connected  whole,  and  you  cannot  modify  one 
part  without  deeply  influencing  all  parts.  This  is  the  law 
of  correlated  variation. 

Herr  Yung  has  made  some  interesting  experiments  on 
tadpoles.  Under  normal  circumstances,  the  relation  of 
females  to  males  is  about  57  to  43.  But  when  the  tadpoles 
were  well  fed  on  beef,  the  proportion  of  females  to  males 
rose  so  as  to  become  78  to  32  ;  and  on  the  highly  nutritious 
flesh  of  frogs  the  proportion  became  92  to  8.  A  highly 
nutritious  diet  and  plenty  of  it  caused  a  very  large  pre- 
ponderance of  females. 

Mrs.  Treat,  in  America,  found  that  if  caterpillars  were 
half-starved  before  entering  upon  the  chrysalis  state,  the 
proportion  of  males  was  much  increased;  while,  if  they 
were  supplied  with  abundant  nutritious  food,  the  proportion 
of  female  insects  was  thereby  largely  increased.  The  same 
law  is  said  to  hold  good  for  mammals.  Favourable  vital 
conditions  are  associated  with  the  birth  of  females;  un- 
favourable, with  that  of  males.  Herr  Ploss  attempts  to 
show  that,  among  human  folk,  in  hard  times  there  are  more 
boys  born;  in  good  times,  more  girls. 


60  Animal  Life  and  Intelligence. 

On  the  whole,  we  may  say  that  there  is  some  evidence 
to  show  that  in  certain  cases  favourable  conditions  of 
temperature,  and  especially  nutrition,  tend  to  increase  the 
number  of  females.  We  have  seen  that  many  animals 
pass  through  a  stage  where  the  reproductive  organs  are  not 
yet  differentiated  into  male  and  female,  while  in  some  there 
is  a  temporary  stage  where  the  outer  parts  of  the  organ 
produce  ova  and  the  inner  parts  sperms.  We  have  also 
seen  that  the  ova  are  cells  where  storage  is  in  excess ;  the 
sperms  are  cells  in  which  fission  is  in  excess.  Favourable 
nutritive  conditions  may,  therefore,  not  incomprehensibly 
lead  to  the  formation  of  well-stored  ova ;  unfavourable 
nutritive  conditions,  on  the  other  hand,  to  the  formation  of 
highly  subdivided  sperms.  By  correlated  variation,*  the 
ova-bearing  or  sperm-bearing  individuals  then  develop  into 
the  often  widely  different  males  and  females. 

*  We  have  seen  that  when  volume  tends  to  outrun  surface,  fission  may 
take  place,  whereby  the  same  volume  has  increased  surface.  But  in  un- 
favourable nutritive  conditions,  the  same  surface  which  had  before  been 
sufficient  for  nutrition  may  become,  under  the  less  favourable  circumstances, 
insufficient,  and  fission  may  again  take  place  to  give  a  larger  absorbent  sur- 
face. Hence,  possibly,  the  connection  between  insufficient  nutriment  and 
highly  subdivided  sperms. 


(     6i     ) 


CHAPTER  IV. 

VAKIATION   AND    NATURAL    SELECTION. 

EVERYTHING,  so  far  as  in  it  lies,  said  Benedict  Spinoza,  tends 
to  persist  in  its  own  being.  This  is  the  law  of  persistence. 
It  forms  the  basis  of  Newton's  First  Law  of  Motion,  which 
enunciates  that,  if  a  body  be  at  rest,  it  will  remain  so  unless 
acted  on  by  some  external  force ;  or,  if  it  be  in  motion,  it 
will  continue  to  move  in  the  same  straight  line  and  at  a 
uniform  velocity  unless  it  is  acted  on  by  some  external 
force.  Practically  every  known  body  is  thus  affected  by 
external  forces ;  but  the  law  of  persistence  is  not  thereby 
disproved.  It  only  states  what  would  happen  under  certain 
exceptional  or  perhaps  impossible  circumstances.  To 
those  ignorant  of  scientific  procedure,  it  seems  unsatis- 
factory, if  not  ridiculous,  to  formulate  laws  of  things,  not  as 
they  are,  but  as  they  might  be.  Many  well-meaning  but 
not  very  well-informed  people  thus  wholly  misunderstand 
and  mistake  the  value  of  certain  laws  of  political  economy, 
because  in  those  laws  (which  are  generalized  statements  of 
fact  under  narrowed  and  rigid  conditions,  and  do  not  pre- 
tend to  be  inculcated  as  rules  of  conduct)  benevolence, 
sentiment,  even  moral  and  religious  duty,  are  intention- 
ally excluded.  These  laws  state  that  men,  under  motives 
arising  out  of  the  pursuit  of  wealth,  will  act  in  such  and 
such  a  way,  unless  benevolence,  sentiment,  duty,  or  some 
other  motive,  lead  them  to  act  otherwise.  Such  laws, 
which  hold  good,  not  for  phenomena  in  their  entirety,  but 
for  certain  isolated  groups  of  facts  under  narrowed  con- 
ditions, are  called  laws  of  the  factors  of  phenomena.  And 
'since  the  complexity  of  phenomena  is  such  that  it  is 


62  Animal  Life  and  Intelligence. 

difficult  for  the  human  mind  to  grasp  all  the  interlacing 
threads  of  causation  at  a  single  glance,  men  of  science 
have  endeavoured  to  isolate  their  several  strands,  and, 
applying  the  principle  of  analysis,  without  which  reasoning 
is  impossible,  to  separate  out  the  factors  and  determine 
their  laws.  In  this  chapter  we  have  to  consider  some  of 
the  factors  of  organic  progress,  and  endeavour  to  determine 
their  laws. 

The  law  of  heredity  may  be  regarded  as  that  of  persistence 
exemplified  in  a  series  of  organic  generations.  When,  as 
in  the  amceba  and  some  other  protozoa,  reproduction  is  by 
simple  fission,  two  quite  similar  organisms  being  thus  pro- 
duced, there  would  seem  to  be  no  reason  why  (modifications 
by  surrounding  circumstances  being  disregarded)  hereditary 
persistence  should  not  continue  indefinitely.  Where,  how- 
ever, reproduction  is  effected  by  the  detachment  of  a  single 
cell  from  a  many- celled  organism,  hereditary  persistence  * 
will  be  complete  only  on  the  condition  that  this  reproductive 
cell  is  in  some  way  in  direct  continuity  with  the  cells  of 
the  parent  organism  or  the  cell  from  which  that  parent 
organism  itself  developed.  And  where,  in  the  higher 
animals,  two  cells  from  two  somewhat  different  parents 
coalesce  to  give  origin  to  a  new  individual,  the  phenomena 
of  hereditary  persistence  are  still  further  complicated  by 
the  blending  of  characters  handed  on  in  the  ovum  and  the 
sperm ;  still  further  complication  being,  perhaps,  produced 
by  the  emergence  in  the  offspring  of  characters  latent  in 
the  parent,  but  derived  from  an  earlier  ancestor.  And  if 
characters  acquired  by  the  parents  in  the  course  of  their 
individual  life  be  handed  on  to  the  offspring,  yet  further 
complication  will  be  thus  introduced. 

It  is  no  matter  for  surprise,  therefore,  that,  notwith- 

*  Samuel  Butler  iu  England,  and  Ewald  Hering  in  Prague,  have  in- 
geniously likened  this  hereditary  persistence  to  "  organic  memory."  What 
are  ordinarily  called  memory,  habit,  instinct,  and  embryonic  reconstruction, 
are  all  referable  to  the  memory  of  organic  matter.  The  analogy,  if  used  with 
due  caution,  is  a  helpful  one,  what  we  call  memory  being  the  psychical  aspect 
(under  certain  special  organic  and  neural  conditions)  of  what  under  the 
physical  aspect  we  call  persistence. 


Variation  and  Natural  Selection.  63 

standing  the  law  of  hereditary  persistence,  variations 
should  occur  in  the  offspring  of  animals.  At  the  same 
time,  it  must  be  remembered  that  the  occurrence  of  varia- 
tions is  not  and  cannot  be  the  result  of  mere  chance ;  but 
that  all  such  variations  are  determined  by  some  internal  or 
external  influences,  and  are  thus  legitimate  and  important 
subjects  of  biological  investigation.  In  the  next  chapter 
we  shall  consider  at  some  length  the  phenomena  of  heredity 
and  the  origin  of  variations.  Here  we  will  accept  them 
without  further  discussion,  and  consider  some  of  their  con- 
sequences. But  even  here,  without  discussing  their  origin, 
we  must  establish  the  fact  that  variations  do  actually  occur. 

Variations  may  be  of  many  kinds  and  in  different 
directions.  In  colour,  in  size,  in  the  relative  develop- 
ment of  different  parts,  in  complexity,  in  habits,  and  in 
mental  endowments,  organisms  or  their  organs  may  vary. 
Observers  of  mammals,  of  birds,  and  of  insects  are  well 
aware  that  colour  is  a  variable  characteristic.  But  these 
colour-variations  are  not  readily  described  and  tabulated. 
In  the  matter  of  size  the  case  is  different.  In  Mr.  Wallace's 
recent  work  on  "  Darwinism  "  a  number  of  observations 
on  size-variations  are  collected  and  tabulated.  As  this  is 
a  point  of  great  importance,  I  propose  to  illustrate  it  some- 
what fully  from  some  observations  I  have  recently  made  of 
the  wing-bones  of  bats.  In  carrying  out  these  observa- 
tions and  making  the  necessary  measurements,  I  have  had 
the  advantage  of  the  kind  co-operation  of  my  friend  Mr. 
Henry  Charbonnier,  of  Clifton,  an  able  and  enthusiastic 
naturalist.* 

The  nature  of  the  bat's  wing  will  be  understood  by 
the  aid  of  the  accompanying  figure  (Fig.  12).  In  the  fore 
limb  the  arm-bone,  or  humerus,  is  followed  by  an  elongated 
bone  composed  of  the  radius  and  ulna.  At  the  outer  end 
of  the  radius  is  a  small,  freely  projecting  digit,  which 
carries  a  claw.  This  answers  to  the  thumb.  Then  follow 
four  long,  slender  bones,  which  answer  to  the  bones  in  the 

*  I  have  also  to  thank  Mr,  Edward  Wilson  for  kindly  giving  me  the 
measurements  of  three  or  four  bats  in  the  Bristol  Museum. 


64  Animal  Life  and  Intelligence. 

palm  of  our  hand.  They  are  the  metacarpals,  and  are 
numbered  n.,  in.,  iv.,  and  v.  in  the  tabulated  figures  in  which 
the  observations  are  recorded.  The  metacarpals  of  the 
second  and  third  digits  run  tolerably  close  together,  and 
form  the  firm  support  of  the  anterior  margin  of  the  wing. 


Fig.  12.— "Wing"  of  bat  (Pipistrette). 

Hu.,  hnmerus,  or  ann-bone;  Ul.,  conjoined  radius  and  ulna,  a  bone  in  the  forearm ;  Po., 
pollex,  answering  to  our  thumb ;  n.,  in.,  iv.,  v.,  second,  third,  fourth,  and  fifth  digits  of  the 
manus,  or  hand.  The  figures  are  placed  near  the  metacarpals,  or  palm-bones.  These  are 
followed  by  the  phalanges.  Ft.,  femur  or  thigh-bone;  Ti.,  tibia,  the  chief  bone  of  the  shank. 
The  digits  of  the  pes,  or  foot,  are  short  and  bear  claws.  C'a.,  calcar. 

Those  of  the  third  and  fourth  make  a  considerable  angle 
with  these  and  with  each  other,  and  form  the  stays  of  the 
mid  part  of  the  wing.  Beyond  the  metacarpals  are  the 
smaller  joints  or  phalanges  of  the  digits,  two  or  three  to 
each  digit.  The  third  digit  forms  the  anterior  point  or 
apex  of  the  wing.  The  fourth  and  fifth  digits  form 
secondary  points  behind  this.  Between  these  points  the 
wing  is  scalloped  into  bays. 

From  the  point  of  the  fifth  or  last  digit  the  leathery 
wing  membrane  sweeps  back  to  the  ankle.  The  bones  of 
the  hind  limb  are  the  femur,  or  thigh-bone,  and  the  tibia 
(with  a  slender,  imperfectly  developed  fibula).  There  are 
five  toes,  which  bear  long  claws.  From  the  ankle  there 
runs  backward  a  long,  bony  and  gristly  spur,  which  serves 


Variation  and  Natural  Selection. 


to  support  the  membrane  which  stretches  from  the  ankle 
to  the  tip  (or  near  the  tip)  of  the  tail. 

Thus  the  wing  of  the  bat  consists  of  a  membrane 
stretched  on  the  expanded  or  spread  fingers  of  the  hand,  and 
sweeping  from  the  point  of  the  little  finger  to  the  ankle. 
Behind  the  ankle  there  is  a  membrane  reaching  to  the  tip 
of  the  tail.  This  forms  a  sort  of  net  in  which  some  bats,  at 
any  rate,  as  I  have  myself  observed,  can  catch  insects. 

I  have  selected  the  wing  of  the  bat  to  exemplify  varia. 
tion,  (1)  because  the  bones  are  readily  measured  even  in 
dried  specimens ;  (2)  because  they  form  the  mutually  related 
parts  of  a  single  organ ;  and  (3)  because  they  offer  facilities 
for  the  comparison  of  variations,  not  only  among  the 
individuals  of  a  single  species,  but  also  among  several 
distinct  species. 

The  method  employed  has  been  as  follows  :  The  several 
bones  have  been  carefully  measured  in  millimetres,*  and 
all  the  bones  tabulated  for  each  species.  Such  tables  of 
figures  are  here  given  in  a  condensed  form  for  three  species 
of  bats. 

BAT-MEASUREMENTS  (IN  MILLIMETRES). 


~  t 

THIRD 

FOURTH 

FIFTH 

fi| 

DIGIT. 

DIGIT. 

DIGIT. 

1 

1 

| 

« 

ges  2,  3. 

rf 

» 

I 

c 

i 

i 

c. 

i 

s« 

jj 

• 

| 

s 

= 

1 

i 

S 

1 

5 

03 

r 

1 

1 

a 

I 

I 

| 

1 

1 

| 

1 

I 

s 
S 

41 

6*5 

88 

40 

16 

1!) 

38 

14 

7 

33 

8 

7 

16 

41 

6 

38 

40 

16 

19 

39 

16-8 

7 

33 

8 

6-5 

16 

Hairy-armed  bat  (  Vespe- 
rugo  leisleri). 

41 
41-5 
40 

6 
5 

6 

39 
39 
39 

40 
37 

16 
17 

15-5 

18 
30 
18 

39 
39 

37 

16 
16 

1-1-5 

6*5 
7 

7 

33 
33 
32 

8 
8 

7 
7  • 

6-e 

16 
15 
15 

41 

5-5 

38-6 

39 

UJT, 

20 

39 

15 

7-5 

33 

g 

7-5 

17 

41 

6 

39 

40 

IB'B 

20*5 

N 

15-f, 

7 

83 

8 

7 

16 

51 

6 

39  . 

M 

19 

39 

40 

11 

18 

40 

13 

15 

22 

Horseshoe  bat  (Ehinolo- 
phus  ferri-equinum'). 

54 
52 
54 

* 
5 
5 

40 
39 

36 
36 
34 

18 
18 
18 

3-2 
32 

40 
39 
40 

11 

10 
11 

19 

19 

17 

4(1 
40 
40 

14 
13 
13 

16 
14 
13 

28 
23 
25 

46 

5 

M 

34 

16 

39 

36 

10 

19 

30 

13 

17 

22 

Lesser     horseshoe     bat  ( 

34 

4 

25 

33 

12 

17 

26 

6-6 

12 

36 

B 

13 

17 

(Rhinoloplius     hipyo-  \ 
sideros).                          ( 

37 
35 

3 
3 

26 

26 

34 

34-0 

13 
13 

30 
17 

28 
37 

8 
7 

13 
12 

28 
36 

9 

10 

14 
13 

17 
15 

It  would  be  troublesome  to  the  reader  to  pick  out  the 
*  A  millimetre  is  about  ^V  of  au  inch,  or  more  exactly  -03937  inch. 


66  Animal  Life  and  Intelligence. 

meaning  from  these  figures.  I  have,  therefore,  plotted  in 
the  measurements  for  four  other  species  of  bats  in  tabular 
form  (Figs.  13,  14,  15,  16). 

Fig.  13,  for  example,  deals  with  the  common  large 
noctule  bat,  which  may  often  be  seen  flying  high  up  on 
summer  evenings.  Now,  the  mean  length  of  the  radius  and 
ulna  in  eleven  individuals  was  51*5  millimetres.  Suppose 
all  the  eleven  bats  had  this  bone  (for  the  two  bones  form 
practically  one  piece)  of  exactly  the  same  length.  There 
would  then  be  no  variation.  We  may  express  this  supposed 
uniformity  by  the  straight  horizontal  line  running  across 
the  part  of  the  figure  dealing  with  the  radius  and  ulna. 
Practically  the  eleven  bats  measured  did  not  have  this 
bone  of  the  same  length ;  in  some  of  them  it  was  longer, 
in  others  it  was  shorter  than  the  mean.  Let  us  run 
through  the  eleven  bats  (which  are  represented  by  the 
numbers  at  the  head  of  the  table)  with  regard  to  this  bone. 
The  first  fell  below  the  average  by  a  millimetre  and  a  half, 
the  length  being  fifty  millimetres.  This  is  expressed  in  the 
table  by  placing  a  dot  or  point  three  quarters  of  a  division 
below  the  mean  line.  Each  division  on  the  table  represents 
two  millimetres,  or,  in  other  words,  the  distance  between 
any  two  horizontal  lines  stands  for  two  millimetres 
measured.  Half  a  division,  therefore,  is  equivalent  to  one 
measured  millimetre ;  a  quarter  of  a  division  to  half  a  milli- 
metre. The  measurements  are  all  made  to  the  nearest  half- 
millimetre.  The  second  bat  fell  short  of  the  mean  by  one 
millimetre.  The  bone  measured  50' 5  millimetres.  The 
third  exceeded  the  mean  by  a  millimetre  and  a  half ;  the 
fourth,  by  three  millimetres  and  a  half.  The  fifth  was  a 
millimetre  and  a  half  above  the  mean ;  and  the  sixth 
and  seventh  were  both  half  a  millimetre  over  the  mean. 
The  eighth  fell  short  by  half  a  millimetre  ;  the  ninth  and 
tenth  by  a  millimetre  and  a  half;  and  the  eleventh  by 
two  millimetres  and  a  half.  The  points  have  been  con- 
nected together  by  lines,  so  as  to  give  a  curve  of  variation 
for  this  bone. 

The  other  curves  in  these  four  tables  are  drawn  in  exactly 


Variation  and  Natural  Selection. 


67 


Gf  9 

72345 


III 

nges  of  Dlg± 


ibia 
mm 


Fig.  13.— The  noctule  (Vesperugo  noctula). 


68 


Animal  Life  and  Intelligence. 


Phalanges  of  Digit 
81-5  mm 


IV 

Phalanges  of  Digit 
18-5  mm   ~ 


V 

Metacarpal 
31  mm 


V 

Phalanges  of  Digit 
18-5  mm 


Tibia 
17-  5  mm 


Fig.  14.— The  long-eared  bat  (Plecotus  auritus). 


Variation  and  Natural  Selection. 


69 


/  23456789  70 


Fig.  15. — The  pipistrelle  (Vesperugo  pipsitrellus). 


Animal  Life  and  Intelligence. 


123       4      S     6        7 


II 

Metacarpal 
28mm 


III 


Phalanges  of  Digit 


24. 5  mm 


IV 

Metacarpal 
28.5mm 


IV 

Phalanges  of  Dig 
16.5  mm 


V 

Metacarpal 
28.5mm 


V 

Phalanges  of  Dig 
14.5  mm 


Tibia 
14.5mm 


10    11    12      13    14    15       18   17    18      19    20 


Fig.  16.— The  whiskered  bat  (Vespertilio  mystacinus). 


Variation  and  Natiiral  Selection.  71 

the  same  way.  The  mean  length  is  stated;  and  the 
amount  by  which  a  bone  in  any  bat  exceeds  or  falls  short 
of  the  mean  can  be  seen  and  readily  estimated  by  means 
of  the  horizontal  lines  of  the  table.  Any  one  can  reconvert 
the  tables  into  figures  representing  our  actual  measurements. 

Now,  it  may  be  said  that,  since  some  bats  run  larger 
than  others,  such  variation  is  only  to  be  expected.  That  is 
true.  But  if  the  bones  of  the  wing  all  varied  equally,  all  the 
curves  would  be  similar.  That  is  clearly  not  the  case.  The 
second  metacarpal  is  the  same  length  in  5  and  6.  But  the 
third  metacarpal  is  two  millimetres  shorter  in  6  than  in  5. 
In  10  the  radius  and  ulna  are  longer  than  in  11 ;  but  the 
second  metacarpal  is  shorter  in  10  than  in  11.  A  simple 
inspection  of  the  table  as  a  whole  will  show  that  there  is  a 
good  deal  of  independent  variation  among  the  bones. 

The  amount  of  variation  is  itself  variable,  and  in  some 
cases  is  not  inconsiderable.  In  the  long-eared  bats  4  and 
5  in  Fig.  14,  the  phalanges  of  the  third  digit  measured  26'5 
millimetres  in  4,  and  34  millimetres  in  5 — a  difference  of 
more  than  28  per  cent.  This  is  unusually  large,  and  it  is 
possible  that  there  may  have  been  some  slight  error  in  the 
measurements.*  A  difference  of  10  or  12  per  cent,  is, 
however,  not  uncommon. 

In  any  case,  the  observations  here  tabulated  show  (1) 
that  variations  of  not  inconsiderable  amount  occur  among 
the  related  bones  of  the  bat's  wing  ;  and  (2)  that  these  varia- 
tions are  to  a  considerable  extent  independent  of  each  other. 

So  far  we  have  compared  a  series  of  individuals  of  the 
same  species  of  bat,  each  table  in  Figs.  13-16  dealing 
with  a  distinct  species.  Let  us  now  compare  the  different 
species  with  each  other.  To  effect  such  a  comparison,  we 
must  take  some  one  bone  as  our  standard,  and  we  must 
level  up  our  bats  for  the  purposes  of  tabulation.  I  have 
selected  the  radius  and  ulna  as  the  standard.  In  both  the 

*  In  nearly  all  cases  the  measurements  were  checked  by  comparing  the 
two  wings.  In  one  or  two  instances  there  were  differences  of  as  much  as  two 
or  three  millimetres  between  the  bones  of  the  two  sides  of  the  body,  but  in 
most  cases  they  exactly  corresponded. 


72  Animal  Life  and  Intelligence. 

noctule  and  the  greater  horseshoe  bats  the  mean  length  of 
this  bone  is  51 '5  millimetres.  The  bones  of  each  of  the 
other  bats  have  been  multiplied  by  such  a  number  as  will 
bring  them  up  to  the  level  of  size  in  these  two  species. 
Mr.  Galton,  in  his  investigations  on  the  variations  of 
human  stature,  had  to  take  into  consideration  the  fact  that 
men  are  normally  taller  than  women.  He  found,  however, 
that  the  relation  of  man  to  woman,  so  far  as  height  is 
concerned,  is  represented  by  the  proportion  108  to  100.  By 
multiplying  female  measurements  by  1*08,  they  were  brought 
up  to  the  male  standard,  and  could  be  used  for  purposes  of 
comparison.  In  the  same  way,  by  multiplying  in  each  case 
by  the  appropriate  number,  I  have  brought  all  the  species 
in  the  table  (Fig.  17)  up  to  the  standard  of  the  noctule. 
When  so  multiplied,  the  radius  and  ulna  (selected  as  the 
standard  of  comparison)  has  the  same  length  in  all  the 
species,  and  is  hence  represented  by  the  horizontal  line  in 
the  table. 

Compared  with  this  as  a  standard,  the  mean  length  of 
the  second  metacarpal  in  the  seven  species  is  forty-three 
millimetres  ;  that  of  the  third  metacarpal,  forty-four  milli- 
metres ;  and  so  on.  The  amount  by  which  each  species 
exceeds  or  falls  short  of  the  mean  is  shown  on  the  table, 
and  the  points  are  joined  up  as  before.  Here,  again,  the 
table  gives  the  actual  measurements  in  each  case.  For 
example,  if  the  mean  length  of  the  third  metacarpal  of  the 
greater  horseshoe  bat  be  required,  it  is  seen  by  the  table 
to  fall  short  of  the  mean  by  four  horizontal  divisions  and 
a  quarter,  that  is  to  say,  by  eight  millimetres  and  a  half. 
The  length  is  therefore  (44  —  8^)  35'5  millimetres. 

Now,  it  will  be  seen  from  the  table  that  the  variation  in 
the  mean  length  of  the  bones  in  different  species  is  much 
greater  than  the  individual  variations  in  the  members  of 
the  same  species.  The  table  also  brings  out  in  an  interest- 
ing way  the  variation  in  the  general  character  of  the  wing. 
The  noctule,  for  example,  is  especially  strong  in  the  de- 
velopment of  the  second  and  third  metacarpals,  the 
phalanges  of  the  third  digit  being  also  a  little  above  the 


Variation  and  Natural  Selection. 


73 


Noctule     Gr.Horse  Shoe  Hairy  Armed   Long  Eared  Lr.Horse  Shoe  Whiskered     Piplstrelle 


Radius  and 

Ulna 
51.5  mm 


Metacarpal 
43  mm 


Metacarpal 
44  mm 


Phalanges  of  Diffi 
43.5  mm 


IV 

Metacarpal 
45  mm 


IV 

Phalanges  of  Digit 
27.5  mm 


Metacarpal 
42  mm 


'"'" 


V 

\ges  of  Digit 
24 


Tibia 
21.5 


Fig.  17.— Variations  adjusted  to  the  standard  of  the  noctule. 


74  Animal  Life  and  Intelligence. 

average.  Eeference  to  the  figure  of  the  bat's  wing  on 
p.  64  will  show  that  these  excellences  give  length  to  the 
wing.  It  fails,  however,  in  the  metacarpal  and  phalanges 
of  the  fifth  digit,  and  in  the  length  of  the  hind  leg  as 
represented  by  the  tibia.  On  consulting  the  figure  of  the 
wing,  it  is  seen  that  these  are  the  bones  which  give  breadth 
to  the  wing.  Here  the  noctule  fails.  Its  wing  is,  therefore, 
long  and  narrow.  It  is  a  swallow  among  bats. 

On  the  other  hand,  the  horseshoe  bats  fail  conspicu- 
ously in  the  second  and  third  metacarpals,  though  they 
make  up  somewhat  in  the  corresponding  digits.  On  the 
whole,  the  wing  is  deficient  in  length.  But  the  phalanges 
of  the  fourth  and  fifth  digits,  and  the  length  of  the  hind 
limb  represented  by  the  tibia,  give  a  corresponding  increase 
of  breadth.  The  wing  is,  therefore,  relatively  short  and 
broad.  The  long-eared  bat,  again,  has  the  third  meta- 
carpal and  its  digits  somewhat  above  the  mean,  and  there- 
fore a  somewhat  more  than  average  length.  But  it  has 
the  fifth  metacarpal  with  its  digit  and  also  the  tibia 
decidedly  above  the  mean,  and  therefore  more  than  average 
breadth.  Without  possessing  the  great  length  of  the 
noctule's  wing,  or  the  great  breadth  of  that  of  the  horse- 
shoe, it  still  has  a  more  than  average  length  and  breadth. 

The  total  wing-areas  are  very  variable,  the  females 
having  generally  an  advantage  over  the  males.  I  do  not 
feel  that  our  measurements  are  sufiiciently  accurate  to 
justify  tabulation.  Taking,  however,  the  radius  and  ulna 
as  the  standard  for  bringing  the  various  species  up  to  the 
same  level,  the  greater  horseshoe  seems  to  have  decidedly 
the  largest  wing-area ;  the  noctule  stands  next ;  then  come 
the  lesser  horseshoe  and  the  long-eared  bat;  somewhat 
lower  stands  the  hairy-armed  bat ;  while  the  pipistrelle 
and  the  whiskered  bat  (both  small  species)  stand  lowest.* 

Sufficient  has  now  been  said  in  illustration  of  the  fact 

*  We  are  anxious  to  extend  our  observations  and  to  compare  series  of  bats 
from  different  localities.  If  any  of  my  readers  should  feel  disposed  to  help  us, 
by  sending  specimens  (with  the  locality  duly  indicated)  to  Mr.  H.  Charbonnier, 
7,  The  Triangle  South,  Clifton,  Bristol,  we  shall  be  grateful. 


Variation  and  Natiiral  Selection.  75 

that  variations  in  the  lengths  of  the  bones  in  the  bat's 
wing  do  actually  occur  in  the  various  individuals  of  one 
species ;  that  the  variations  are  independent ;  and  that  the 
different  species  and  genera  have  the  character  of  the  wing 
determined  by  emphasizing,  so  to  speak,  variations  in 
special  directions.  I  make  no  apology  for  having  treated 
the  matter  at  some  length.  Those  who  do  not  care  for 
details  will  judiciously  exercise  their  right  of  skipping. 

As  before  mentioned,  Mr.  Wallace  has  collected  and 
tabulated  other  observations  on  size  and  length  variations. 
And  in  addition  to  such  variations,  there  are  the  numerous 
colour-variations  that  do  not  admit  of  being  so  readily 
tabulated.  Mr.  Cockerell  tells  us  that  among  snail-shells, 
taking  variations  of  banding  alone,  he  knows  of  252 
varieties  of  Helix  nemoralis  and  128  of  H.  hortensis.* 

That  variations  do  occur  under  nature  is  thus  un- 
questionable. And  it  is  clear  that  all  variations  necessarily 
fall  under  one  of  three  categories.  Either  they  are  of 
advantage  to  the  organism  in  which  they  occur ;  or  they  are 
disadvantageous  ;  or  they  are  neutral,  neither  advantageous 
nor  disadvantageous  to  the  animal  in  its  course  through  life. 

We  must  next  revert  to  the  fact  to  which  attention  was 
drawn  in  the  last  chapter,  that  every  species  is  tending, 
through  natural  generation,  to  increase  in  numbers.  Even 
in  the  case  of  the  slow-breeding  elephant,  the  numbers  tend 
to  increase  threefold  in  each  generation ;  for  a  single  pair 
of  elephants  give  birth  to  three  pairs  of  young.  In  many 
animals  the  tendency  is  to  increase  ten,  twenty,  or  thirty- 
fold  in  every  generation ;  while  among  fishes,  amphibians, 
and  great  numbers  of  the  lower  organisms,  the  tendency  is 
to  multiply  by  a  hundredfold,  a  thousandfold,  or  even  in 
some  cases  ten  thousandfold.  But,  as  before  noticed,  this 
is  only  a  tendency.  The  law  of  increase  is  a  law  of  one 
factor  in  life's  phenomena,  the  reproductive  factor.  In  any 

*  Nature,  vol.  xli.  p.  393.  The  variation  in  molluscs  is  often  considerable. 
In  one  of  the  bays  in  the  basement  hall  of  the  Natural  History  Museum  is 
a  series  showing  the  variation  in  size,  form,  and  sculpturing  of  Paludomus 
loricatus,  which  is  found  in  the  streams  of  Ceylon.  These  varieties  have  in 
former  times  been  named  as  ten  distinct  species  ! 


76  Animal  Life  and  Intelligence. 

area,  the  conditions  of  which  are  not  undergoing  change, 
the  numbers  of  the  species  which  constitute  its  fauna 
remain  tolerably  constant.  They  are  not  actually  increasing 
in  geometrical  progression.  There  is  literally  no  room  for 
such  increase.  The  large  birth-rate  of  the  constituent 
species  is  accompanied  by  a  proportionate  death-rate,  or 
else  the  tendency  is  kept  in  check  by  the  prevention  of 
certain  individuals  from  mating  and  bearing  young.* 

Now,  the  high  death-rate  is,  to  a  large  extent  among 
the  lower  organisms  and  in  a  less  degree  among  higher 
animals,  the  result  of  indiscriminate  destruction.  When 
the  ant-bear  swallows  a  tongue-load  of  ants,  when  the 
Greenland  whale  engulfs  some  hundreds  of  thousands  of 
fry  at  a  gulp,  when  the  bear  or  the  badger  destroys  whole 
nests  of  bees, — in  such  cases  there  is  wholesale  and  indis- 
criminate destruction.  Those  which  are  thus  destroyed  are 
nowise  either  better  or  worse  than  those  which  escape.  At 
the  edge  of  a  coral  reef  minute,  active,  free-swimming  coral 
embryos  are  set  free  in  immense  numbers.  Presently  they 
settle  down  for  life.  Some  settle  on  a  muddy  bottom, 
others  in  too  great  a  depth  of  water.  These  are  destroyed. 
The  few  which  take  up  a  favourable  position  survive.  But 
they  are  no  better  than  their  less  fortunate  neighbours. 
The  destruction  is  indiscriminate.  So,  too,  among  fishes 

*  More  observations  and  fuller  knowledge  on  this  latter  point  and  on  the 
relative  numbers  of  the  sexes  in  different  species  are  much  to  be  desired.  It 
is  clear  that  the  number  of  offspring  mainly  depends  upon  the  number  of 
females.  But  if  it  be  true  that  good  times  and  favourable  conditions  lead 
to  an  increased  production  of  females,  while  hard  times  and  unfavourable 
conditions  lead  to  a  relative  increase  of  males,  then  it  is  evident  that  good 
times  will  lead  to  a  more  rapid  increase  and  hard  times  to  a  less  rapid  increase 
of  the  species.  Suppose,  for  example,  in  a  particular  district  food  and  other 
conditions  were  especially  favourable  for  frogs.  Among  the  well-nourished 
tadpoles  there  would  be  a  preponderance  of  females.  In  the  next  generation 
the  many  females  would  produce  abundant  offspring  (for  one  male  may 
fertilize  the  ova  laid  by  several  females).  There  would  be  a  greater  number 
of  tadpoles  to  compete  for  the  same  amount  of  nutriment.  They  would  be 
less  nourished.  There  would  be  less  females ;  and  in  the  succeeding  genera- 
tion a  diminished  number  of  tadpoles.  Thus  to  some  extent  a  balance  between 
the  number  of  tadpoles  and  the  amount  of  available  nutrition  would  be  main- 
tained. These  conclusions  are,  perhaps,  too  theoretical  to  be  of  much  value, 
while  the  tendency  here  indicated  would  be  but  one  factor  among  many. 


Variation  and  Natural  Selection.  77 

and  the  many  marine  forms  which  produce  a  great  number 
of  fertilized*eggs  giving  rise  to  embryos  that  are  from  an 
early  period  free-swimming  and  self-supporting.  Such 
embryos  are  decimated  by  a  destruction  which  is  quite 
indiscriminate.  And  again,  to  take  but  one  more  example, 
the  liver-fluke,  whose  life-history  was  sketched  in  the  last 
chapter,  produces  its  tens  or  hundreds  of  thousands  of 
ova.  But  the  chances  are  enormously  against  their  com- 
pleting their  life-cycle.  If  the  conditions  of  temperature 
and  moisture  are  not  favourable,  the  embryo  is  not  hatched 
or  soon  dies ;  even  if  it  emerges,  no  further  development 
takes  place  unless  it  chances  to  come  in  contact  with  a 
particular  and  not  very  common  kind  of  water-snail.  When 
it  emerges  from  the  intermediate  host  and  settles  on  a 
blade  of  grass,  it  must  still  await  the  chance  of  that  blade 
being  eaten  by  a  sheep  or  goat.  It  is  said  that  the  chances 
are  eight  millions  to  one  against  it,  and  for  the  most  part 
its  preservation  is  due  to  no  special  excellence  of  its  own. 
The  destruction  is  to  a  large  extent,  though  not  entirely, 
indiscriminate. 

Even  making  all  due  allowance,  however,  for  this  indis- 
criminate destruction — which  is  to  a  large  extent  avoided 
by  those  higher  creatures  which  foster  their  young — there 
remain  more  individuals  than  suffice  to  keep  up  the  normal 
numbers  of  the  species.  Among  these  there  arises  a 
struggle  for  existence,  and  hence  what  Darwin  named 
natural  selection. 

"  How  will  the  struggle  for  existence  " — I  quote,  with 
some  omissions,  the  words  of  Darwin — "  act  in  regard  to 
variation  ?  Can  the  principle  of  selection,  which  is  so 
potent  in  the  hands  of  man,  apply  under  nature  ?  I  think 
that  we  shall  see  that  it  can  act  most  efficiently.  Let  the 
endless  number  of  slight  variations  and  individual  differ- 
ences be  borne  in  mind;  as  well  as  the  strength  of  the 
hereditary  tendency.  Let  it  also  be  borne  in  mind  how 
infinitely  complex  and  close-fitting  are  the  mutual  relations 
of  all  organic  beings  to  each  other  and  to  their  physical 
conditions  of  life  ;  and  consequently  what  infinitely  varied 


78  Animal  Life  and  Intelligence. 

diversities  of  structure  might  be  of  use  to  each  being  under 
changing  conditions  of  life.  Can  it,  then,  be  thought 
improbable,  seeing  that  variations  useful  to  man  have 
undoubtedly  occurred,  that  other  variations,  useful  in  some 
way  to  each  being  in  the  great  and  complex  battle  of  life, 
should  occur  in  the  course  of  many  successive  generations  ? 
If  such  do  occur,  can  we  doubt  (remembering  that  many 
more  individuals  are  born  than  can  possibly  survive)  that 
individuals  having  any  advantage,  however  slight,  over 
others,  would  have  the  best  chance  of  surviving  and  of 
procreating  their  kind  ?  On  the  other  hand,  we  may  feel 
sure  that  any  variation  in  the  least  degree  injurious  would 
be  rigidly  destroyed.  This  preservation  of  favourable  indi- 
vidual differences  and  variations,  and  the  destruction  of 
those  which  are  injurious,  I  have  called  Natural  Selection, 
or  the  Survival  of  the  Fittest.  Variations  neither  useful 
nor  injurious  would  not  be  affected  by  natural  selection, 
and  would  be  left  either  a  fluctuating  element,  or  would 
ultimately  become  fixed,  owing  to  the  nature  of  the 
organism  and  the  nature  of  the  conditions."  * 

"  The  principle  of  selection,"  says  Darwin,  elsewhere, 
"  may  conveniently  be  divided  into  three  kinds.  Methodical 
selection  is  that  which  guides  a  man  who  systematically 
endeavours  to  modify  a  breed  according  to  some  pre- 
determined standard.  Unconscious  selection  is  that  which 
follows  from  men  naturally  preserving  the  most  valued 
and  destroying  the  less  valued  individuals,  without  any 
thought  of  altering  the  breed.  Lastly,  we  have  Natural 
selection,  which  implies  that  the  individuals  which  are  best 
fitted  for  the  complex  and  in  the  course  of  ages  changing 
conditions  to  which  they  are  exposed,  generally  survive 
and  procreate  their  kind."  f 

I  venture  to  think  that  there  is  a  more  logical  division 
than  this.  A  man  who  is  dealing  with  animals  or  plants 
under  domestication  may  proceed  by  one  of  two  well-con- 
trasted methods.  He  may  either  select  the  most  satisfac- 

*  "  Origin  of  Species,"  pp.  62,  63. 

t  "  Animals  and  Plants  under  Domestication,"  vol.  it  p.  177. 


Variation  and  Natural  Selection.  79 

tory  individuals  or  he  may  reject  the  most  unsatisfactory. 
We  may  term  the  former  process  selection,  the  latter 
elimination.  Suppose  that  a  gardener  is  dealing  with  a 
bed  of  geraniums.  He  may  either  pick  out  first  the  best, 
then  the  second  best,  then  the  third,  and  so  on,  until  he 
has  selected  as  many  as  he  wishes  to  preserve.  Or,  on 
the  other  hand,  he  may  weed  out  first  the  worst,  then  in 
succession  other  unsatisfactory  stocks,  until,  by  eliminating 
the  failures,  he  has  a  residue  of  sufficiently  satisfactory 
flowers.  Now,  I  think  it  is  clear  that,  even  if  the  ultimate 
result  is  the  same  (if,  that  is  to  say,  he  selects  the  twenty 
best,  or  eliminates  all  but  the  twenty  best),  the  method  of 
procedure  is  in  the  two  cases  different.  Selection  is  applied 
at  one  end  of  the  scale,  elimination  at  the  other.  There  is 
a  difference  in  method  in  picking  out  the  wheat-grains  (like 
a  sparrow)  and  scattering  the  chaff  by  the  wind. 

Under  nature  both  methods  are  operative,  but  in  very 
different  degrees.  Although  the  insect  may  select  the 
brightest  flowers,  or  the  hen-bird  the  gaudiest  or  most 
tuneful  mate,  the  survival  of  the  fittest  under  nature  is  in 
the  main  the  net  result  of  the  slow  and  gradual  process  of 
the  elimination  of  the  unfit.*  The  best-adapted  are  not, 
save  in  exceptional  cases,  selected ;  but  the  ill-adapted  are 
weeded  out  and  eliminated.  And  this  distinction  seems  to 
me  of  sufficient  importance  to  justify  my  suggestion  that 
natural  selection  be  subdivided  under  two  heads — natural 
elimination,  of  widespread  occurrence  throughout  the 
animal  world ;  and  selection  proper,  involving  the  element 
of  individual  or  special  choice. 

The  term  "  natural  elimination  "  for  the  major  factor 
serves  definitely  to  connect  the  natural  process  with  that 
struggle  for  existence  out  of  which  it  arises.  The  struggle 
for  existence  is  indeed  the  reaction  of  the  organic  world 
called  forth  by  the  action  of  natural  elimination.  Organisms 
are  tending  to  increase  in  geometrical  ratio.  There  is  not 

*  I  may  here  draw  attention  to  the  fact  that  the  bats  whose  wing-bone 
measurements  were  given  above  are  those  which  have  so  far  survived  and 
escaped  such  elimination  as  is  now  in  progress. 


80  Animal  Life  and  Intelligence. 

room  or  subsistence  for  the  many  born.  The  tendency  is 
therefore  held  in  check  by  elimination,  involving  the  struggle 
for  existence.  And  the  factors  of  elimination  are  three : 
first,  elimination  through  the  action  of  surrounding  physical 
or  climatic  conditions,  under  which  head  we  may  take  such 
forms  of  disease  as  are  not  due  to  living  agency ;  secondly, 
elimination  by  enemies,  including  parasites  and  zymotic 
diseases ;  and  thirdly,  elimination  by  competition.  It  will 
be  convenient  to  give  some  illustrative  examples  of  each  of 
these. 

Elimination  through  the  action  of  surrounding  physical 
conditions,  taken  generally,  deals  with  the  very  groundwork 
or  basis  of  animal  life.  There  are  certain  elementary 
mechanical  conditions  which  must  be  fulfilled  by  every 
organism  however  situated.  Any  animal  which  fails  to 
fulfil  these  conditions  will  be  speedily  eliminated.  There 
are  also  local  conditions  which  must  be  adequately  met. 
Certain  tropical  animals,  if  transferred  to  temperate  or 
sub-Arctic  regions,  are  unable  to  meet  the  requirements  of 
the  new  climatic  conditions,  and  rapidly  or  gradually  die. 
Fishes  which  live  under  the  great  pressure  of  the  deep  sea 
are  killed  by  the  expansion  of  the  gases  in  their  tissues 
when  they  are  brought  to  the  surface.  Many  fresh-water 
animals  are  killed  if  the  lake  in  which  they  live  be  invaded 
by  the  waters  of  the  sea.  If  the  water  in  which  corals  live 
be  too  muddy,  too  cold,  or  too  fresh — near  the  mouth  of  a 
great  river  on  the  Australian  coast,  for  example — they  will 
die  off.  During  the  changes  of  climate  which  preceded 
and  followed  the  oncoming  of  the  glacial  epoch,  there  must 
have  been  much  elimination  of  this  order.  Even  under 
less  abnormal  conditions,  the  principle  is  operative.  Darwin 
tells  us  that  in  the  winter  of  1854-5  four-fifths  of  the 
birds  in  his  grounds  perished  from  the  severity  of  the 
weather,  and  we  cannot  but  suppose  that  those  who  were 
thus  eliminated  were  less  able  than  others  to  cope  with  or 
stand  the  effects  of  the  inclement  climatic  conditions.  My 
colleague,  Mr.  G.  Munro  Smith,  informs  me  that,  in  culti- 
vating microbes,  certain  forms,  such  as  Bacillus  violaceus 


Variation  and  Natural  Selection.  81 

and  Micrococcus  prodigiosus,  remain  in  the  field  during 
cold  weather  when  other  less  hardy  microbes  have  perished. 
The  insects  of  Madeira  may  fairly  be  regarded  as  affording 
another  instance.  The  ground-loving  forms  allied  to 
insects  of  normally  slow  and  heavy  flight  have  in  Madeira 
become  wingless  or  lost  all  power  of  flight.  Those  which 
attempted  to  fly  have  been  swept  out  to  sea  by  the  winds, 
and  have  thus  perished ;  those  which  varied  in  the  direction 
of  diminished  powers  of  flight  have  survived  this  eliminating 
process.  On  the  other  hand,  among  flower-frequenting 
forms  and  those  whose  habits  of  life  necessitate  flight,  the 
Madeira  insects  have  stronger  wings  than  their  mainland 
allies.  Here,  since  flight  could  not  be  abandoned  without 
a  complete  change  of  life-habit,  since  all  must  fly,  those 
with  weaker  powers  on  the  wing  have  been  eliminated, 
leaving  those  with  stronger  flight  to  survive  and  procreate 
their  kind.*  In  Kerguelen  Island  Mr.  Eaton  has  found 
that  all  the  insects  are  incapable  of  flight,  and  most  of  them 
in  a  more  or  less  wingless  condition.!  Mr.  Wallace  regards 
the  reduction  in  the  size  of  the  wing  in  the  Isle  of  Man 
variety  of  the  small  tortoiseshell  butterfly  as  due  to  the 
gradual  elimination  of  larger-winged  individuals.^:  These 
are  cases  of  elimination  through  the  direct  action  of  sur- 
rounding physical  conditions.  Even  among  civilized 
human  folk,  this  form  of  elimination  is  still  occasionally 
operative — in  military  campaigns,  for  example  (where  the 
mortality  from  hardships  is  often  as  great  as  the  mortality 
from  shot  or  steel),  in  Arctic  expeditions,  and  in  arduous 
travels.  But  in  early  times  and  among  savages  it  must  be 
a  more  important  factor. 

Elimination  by  enemies  needs  somewhat  fuller  exempli' 
fication.  Battle  within  battle  must,  throughout  nature, 
as  Darwin  says,  be  continually  recurring  with  varying 
success.  The  stronger  devour  the  weaker,  and  wage  war 
with  each  other  over  the  prey.  In  the  battle  among  co- 
ordinates the  weaker  are  eliminated,  the  stronger  prevail. 

*  "  Origin  of  Species,"  p.  109.  f  "  Darwinism,"  p.  106. 

J  Ibid.  p.  106. 


82  Animal  Life  and  Intelligence. 

When  the  weaker  are  preyed  upon  by  the  stronger  and  a 
fair  fight  is  out  of  the  question,  the  slow  and  heavy  succumb, 
the  agile  and  swift  escape ;  stupidity  means  elimination, 
cunning,  survival ;  to  be  conspicuous,  unless  it  be  for  some 
nasty  or  deleterious  quality,  is  inevitably  to  court  death  : 
the  sober-hued  stand  at  an  advantage.  In  these  cases,  if 
there  be  true  selection  at  work,  it  is  the  selection  of  certain 
individuals,  the  plumpest  and  most  toothsome  to  wit,  for 
destruction,  not  for  survival. 

This  mode  of  elimination  has  been  a  factor  in  the 
development  of  protective  resemblance  and  so-called 
mimicry,  and  we  may  conveniently  illustrate  it  by  reference 
to  these  qualities.  If  the  hue  of  a  creature  varies  in  the 
direction  of  resemblance  to  the  normal  surroundings,  it  will 
render  the  animal  less  conspicuous,  and  therefore  less  liable 
to  be  eliminated  by  enemies.  This  is  well  seen  in  the 
larvae  or  caterpillars  of  many  of  our  butterflies  and  moths. 
It  is  not  easy  to  distinguish  the  caterpillar  of  the  clouded 
yellow,  so  closely  does  its  colour  assimilate  to  the  clover 
leaves  on  which  it  feeds,  nor  that  of  the  Lulworth  skipper 
on  blades  of  grass.  I  would  beg  every  visitor  to  the 
Natural  History  Museum  at  South  Kensington  to  look 
through  the  drawers  containing  our  British  butterflies  and 
moths  and  their  larvae,  in  the  further  room  on  the  base- 
ment, behind  the  inspiring  statue  of  Charles  Darwin.  Half 
an  hour's  inspection  will  serve  to  bring  home  the  fact  of 
protective  resemblance  better  than  many  words. 

It  may,1  however,  be  remarked  that  not  all  the  cater- 
pillars exhibit  protective  resemblance ;  and  it  may  be 
asked — How  have  some  of  these  conspicuous  larvae,  that  of 
the  magpie  moth,  for  example,  escaped  elimination  ?  What 
is  sauce  for  the  Lulworth  goose  should  be  sauce  for  the 
magpie  gander.  How  is  it  that  these  gaudy  and  variable 
caterpillars,  cream-coloured  with  orange  and  black  mark- 
ings, have  escaped  speedy  destruction  ?  Because  they  are 
so  nasty.  No  bird,  or  lizard,  or  frog,  or  spider  would  touch 
them.  They  oan  therefore  afford  to  be  bright-coloured. 
Nay,  their  very  gaudiness  is  an  advantage,  and  saves  them 


Variation  and  Natural  Selection.  83 

from  being  the  subject  of  unpleasant  experiments  in  the 
matter.  Other  caterpillars,  like  the  palmer-worms,  are 
protected  by  barbed  hairs  that  are  intensely  irritating. 
They,  too,  can  afford  to  be  conspicuous.  But  a  sweet  and 
edible  caterpillar,  if  conspicuous,  is  eaten,  and  thus  by  the 
elimination  of  the  conspicuous  the  numerous  dull  green  or 
brown  larvao  have  survived. 

A  walk  through  the  Bird  Gallery  in  the  National 
collection  will  afford  examples  of  protective  resemblance 
among  birds.  Look,  for  example,  at  the  Kentish  plover 
with  its  eggs  and  young — faithfully  reproduced  in  our 
frontispiece — and  the  way  in  which  the  creature  is  thus 
protected  in  early  stages  of  its  life  will  be  evident.  The 
stone-curlew,  the  ptarmigan,  and  other  birds  illustrate  the 
same  fact,  which  is  also  seen  with  equal  clearness  in  many 
mammals,  the  hare  l^eing  a  familiar  example. 

Many  oceanic  organisms  are  protected  through  general 
resemblance.  Some,  like  certain  medusae,  are  transparent. 
The  pellucid  or  transparent  sole  of  the  Pacific  (Achirus 
pellucidus),  a  little  fish  about  three  inches  long,  is  so  trans- 
parent that  sand  and  seaweed  can  be  seen  distinctly 
through  its  tissues.  The  salpa  is  transparent  save  for  the 
intestine  and  digestive  gland,  which  are  brown,  and  look 
like  shreds  of  seaweed.  Other  forms,  like  the  physalia, 
are  cserulean  blue.  The  exposed  parts  of  flat-fish  are 
brown  and  sandy  coloured  or  speckled  like  the  sea-bottom ; 
and  in  some  the  sand-grains  seem  to  adhere  to  the  skin. 
So,  too,  with  other  fish.  "  Looking  down  on  the  dark  back 
of  a  fish,"  says  Mr.  A.  R.  Wallace,  "  it  is  almost  invisible, 
while  to  an  enemy  looking  up  from  below,  the  light  under 
surface  would  be  equally  invisible  against  the  light  of 
clouds  and  sky."  Even  some  of  the  most  brilliant  and 
gaudiest  fish,  such  as  the  coral-fish  (Chcstodon,  Platyglossus, 
and  others),  are  brightly  coloured  in  accordance  with  the 
beautiful  tints  of  the  coral-reefs  which  form  their  habitat  ; 
the  bright-green  tints  of  some  tropical  forest  birds  being 
of  like  import.  No  conception  of  the  range  of  protective 
.resemblance  can  be  formed  when  the  creatures  are  seen 


84  Animal  Life  and  Intelligence. 

or  figured  isolated  from  their  surroundings.  The  zehra  is 
a  sufficiently  conspicuous  animal  in  a  menagerie  or  a 
museum ;  and  yet  Mr.  Galton  assures  us  that,  in  the  bright 
starlight  of  an  African  night,  you  may  hear  one  breathing 
close  by  you,  and  be  positively  unable  to  see  the  animal. 
A  black  animal  would  be  visible ;  a  white  animal  would  be 
visible ;  but  the  zebra's  black  and  white  so  blend  in  the 
dusk  as  to  render  him  inconspicuous. 

To  cite  but  one  more  example,  this  time  from  the 
invertebrates.  Professor  Herdman  found  in  a  rock-pool 
on  the  west  coast  of  Scotland  "  a  peculiarly  coloured  speci- 
men of  the  common  sea-slug  (Doris  tuberculata) .  It  was 
lying  on  a  mass  of  volcanic  rock  of  a  dull-green  colour, 
partially  covered  with  rounded  spreading  patches  of  a 
purplish  pink  nullipore,  and  having  numerous  whitish 
yellow  Spirorbis  shells  scattered  over  it — the  general  effect 
being  a  mottled  surface  of  dull  green  and  pink  peppered 
over  with  little  cream-coloured  spots.  The  upper  surface 
of  the  Doris  was  of  precisely  the  same  colours  arranged  in 
the  same  way.  .  .  .  We  picked  up  the  Doris,  and  remarked 
the  brightness  and  the  unusual  character  of  its  markings, 
and  then  replaced  it  upon  the  rock,  when  it  once  more 
became  inconspicuous."  * 

Then,  too,  there  are  some  animals  with  variable  pro- 
tective resemblance — the  resemblance  changing  with  a 
changing  environment.  This  is  especially  seen  in  some 
Northern  forms,  like  the  Arctic  hare  and  fox,  which  change 
their  colour  according  to  the  season  of  the  year,  being 
brown  in  summer,  white  and  snowy  in  winter.  The  chamse- 
leon  varies  in  colour  according  to  the  hue  of  its  surround- 
ings through  the  expansion  and  contraction  of  certain 
pigment-cells ;  while  frogs  and  cuttle-fish  have  similar  but 
less  striking  powers.  Mr.  E.  B.  Poulton'sf  striking  and 
beautiful  experiments  show  that  the  colours  of  caterpillars 

*  Proceedings  Liverpool  Biological  Society,  1889. 

t  Since  this  chapter  was  written,  Mr.  Poulton  has  published  his  interesting 
and  valuable  work  on  "The  Colours  of  Animals,"  from  which  I  have  con- 
trived to  insert  one  or  two  additional  examples. 


Variation  and  Natural  Selection.  85 

and  chrysalids  reared  from  the  same  brood  will  vary  accord- 
ing to  the  colour  of  their  surroundings. 

If  this  process  of  protective  resemblance  be  carried  far, 
the  general  resemblance  in  hue  may  pass  into  special 
resemblance  to  particular  objects.  The  stick-insect  and 


Fig.  18. — Caterpillar  of  a  moth  (Ennomos  tiliaria)  on  an  oak-spray.     (From 
an  exhibit  iu  the  British  Natural  History  Museum.) 

the  leaf-insect  are  familiar  illustrations,  though  no  one 
who  has  not  seen  them  in  nature  can  realize  the  extent  of 
the  resemblance.  Most  of  us  have,  at  any  rate,  seen  the 
stick-caterpillars,  or  loopers  (Fig.  18),  though,  perhaps,  few 


86  Animal  Life  and  Intelligence. 

have  noticed  how  wonderful  is  the  protective  resemblance 
to  a  twig  when  the  larva  is  still  and  motionless,  for  the 
very  reason  that  the  resemblance  is  so  marked  that  the 
organism  at  that  time  escapes,  not  only  casual  observation, 
but  even  careful  search.  Fig.  19  gives  a  representation 
of  a  locust  with  special  protective  resemblance  to  a  leaf — 
not  a  perfect  leaf,  but  a  leaf  with  fungoid  blotches.  This 
insect  and  the  stick-caterpillar  may  be  seen  in  the  insect 
exhibits  on  the  basement  at  South  Kensington,  having 
been  figured  from  them  by  the  kind  permission  of  Professor 
Flower. 


Fig.  19. — A  locust  (Cycloptera  speculata)  which  closely  resembles  a  leaf. 
(From  an  exhibit  in  the  British  Natural  History  Museum.) 

Perhaps  one  of  the  most  striking  instances  of  special 
protective  resemblance  is  that  of  the  Malayan  leaf-butterfly 
(Kallima  paralecta).  So  completely,  when  the  wings  are 
closed,  does  this  insect  resemble  a  leaf  that  it  requires  a 
sharp  eye  to  distinguish  it.  These  butterflies  have,  more- 
over, the  habit  of  alighting  very  suddenly.  As  a  recent 
observer  (Mr.  S.  B.  T.  Skertchly)  remarks,  they  "  fly  rapidly 
along,  as  if  late  for  an  appointment,  suddenly  pitch,  close 
their  wings,  and  become  leaves.  It  is  generally  done  so 
rapidly  that  the  insect  seems  to  vanish."  *  Instances  might 

*  Ann.  and  Mag.  Nat.  Hist.,  September,  1889,  p..  209,  quoted  by  Poulton, 
"  Colours  of  Animals,"  p.  55. 


Variation  and  Natural  Selection.  87 

be  multiplied  indefinitely.  Mr.  Guppy  thus  describes  a 
species  of  crab  in  the  Solomon  Islands  :  "  The  light  purple 
colour  of  its  carapace  corresponds  with  the  hue  of  the  coral 
at  the  base  of  the  branches,  where  it  lives  ;  whilst  the  light 
red  colour  of  the  big  claws,  as  they  are  held  up  in  their 
usual  attitude,  similarly  imitates  the  colour  of  the  branches. 
To  make  the  guise  more  complete,  both  carapace  and  claws 
possess  rude  hexagonal  markings  which  correspond  exactly 
in  size  and  appearance  with  the  polyp-cells  of  the  coral."  * 

When  the  special  protective  resemblance  is  not  to  an 
inanimate  object,  but  to  another  organism,  it  is  termed 
mimicry.  It  arises  in  the  following  way : — 

Many  forms,  especially  among  the  invertebrates,  escape 
elimination  by  enemies  through  the  development  of  offen- 
sive weapons  (stings  of  wasps  and  bees),  a  bitter  taste  (the 
Heliconidae  among  butterflies),  or  a  hard  external  covering 
(the  weevils  among  beetles).  The  animals  which  prey 
upon  these  forms  learn  to  avoid  these  dangerous,  nasty, 
or  indigestible  creatures  ;  and  the  avoidance  is  often  in- 
stinctive. It  thus  becomes  an  advantage  to  other  forms, 
not  thus  protected,  to  resemble  the  animals  that  have  these 
characteristics.  Such  resemblance  is  termed  mimicry, 
concerning  which  it  must  be  remembered  that  the  mimicry 
is  unconscious,  and  is  reached  by  the  elimination  of  those 
forms  which  do  not  possess  this  resemblance.  Thus  tlie 
Leptalis,  a  perfectly  sweet  insect,  closely  resembles  the 
Methona,  a  butterfly  producing  an  ill-smelling  yellow  fluid. 
The  quite  harmless  Clytus  arietis,  a  beetle,  resembles,  not 
only  in  general  appearance,  but  in  its  fussy  walk,  a 
wasp.  The  soft-skinned  Dollops,  a  longicorn,  resembles  the 
strongly  encased  Pachyrhyncus  orUfex,  a  weevil.  The  not 
uncommon  fly  Eristalis  tenax  (Fig.  20),  is  not  unlike  a  bee, 
and  buzzes  in  an  unpleasantly  suggestive  manner.f 

*  Nature,  vol.  xxxv.  p.  77. 

f  Many  other  instances  might  be  added.  The  hornet  clear-wing  moth 
(Sphecia  apiformis)  mimics  the  hornet  or  wasp;  the  narrow-bordered  bee- 
hawk  moth  (Sesia  ~bombyliformis)  mimics  a  bumble-bee.  These  insects  may 
be  seen  in  the  lepidoptera  drawers  in  the  Natural  History  Museum.  But 
perhaps  the  most  wonderful  instance  of  insect-mimicry  is  that  observed 


Animal  Life  and  Intelligence. 


Mimicry  is  not  confined  to  the  Invertebrates.  A  harm- 
less snake,  the  eiger-eter  of  Dutch  colonists  at  the  Cape, 
subsists  mainly  or  entirely  on  eggs.  The  mouth  is  almost 
or  quite  toothless ;  but  in  the  throat  hard-tipped  spines 
project  into  the  gullet  from  the  vertebrae  of  the  column  in 
this  region.  Here  the  egg  is  broken,  and  there  is  no  fear 
of  losing  the  contents.  Now,  there  is  one  species  of  this 
snake  that  closely  resembles  the  berg-adder.  The  head 
has  naturally  the  elongated  form  characteristic  of  the 
harmless  snakes.  But  when  irritated,  this  egg-eater  flattens 
it  out  till  it  has  the  usual  viperine  shape  of  the  "  club  " 
on  a  playing-card.  It  coils  as  if  for  a  spring,  erects  its 
head  with  every  appearance  of  anger,  hisses,  and  darts 
forward  as  if  to  strike  its  fangs  into  its  foe,  in  every  way 
imitating  an  enraged  berg-adder.  The  snake  is,  however, 
quite  harmless  and  inoffensive.* 

Here  we  have  mimicry  both  in  form  and  habit.  Another 
case  of  imperfect  but  no  doubt  effectual  mimicry  is  given 
by  Mr.  W.  Larden,  in  some  notes  from  South  America. f 
Speaking  of  the  rhea,  or  South  American  ostrich,  he 
says,  "  One  day  I  came  across  an  old  cock  in  a  nest  that 
it  had  made  in  the  dry  weeds  and  grass.  Its  wings  and 
feathers  were  loosely  arranged,  and  looked  not  unlike  a 
heap  of  dried  grass  ;  at  any  rate,  the  bird  did  not  attract 
my  attention  until  I  was  close  on  him.  The  long  neck  was 
stretched  out  close  along  the  ground,  the  crest  feathers 
were  flattened,  and  an  appalling  hiss  greeted  my  approach. 
It  was  a  pardonable  mistake  if  for  a  moment  I  thought 
I  had  come  across  a  huge  snake,  and  sprang  back  hastily 
under  this  impression." 

Protective  resemblance  and  mimicry  have  been  con- 
by  Mr.  W.  L.  Sclater,  and  given  by  Mr.  E.  B.  Ponlton,  in  his  "  Colours  of 
Animals  "  (p.  252),  where  a  (probably)  homopterous  insect  mimics  a  leaf-cutting 
ant,  together  with  its  leafy  burden — a  membranous  expansion  in  the  mimic 
closely  resembling  the  piece  of  leaf  carried  by  the  particular  kind  of  ant  he 
resembles. 

*  The  late  Mr.  H.  "W.  Oakley  .first  drew  my  attention  to  this  snake. 
Since  then  Mr.  Hammond  Tooke  has  described  the  facts  in  Nature,  vol.  xxxiv. 
p.  547. 

f  Nature,  vol.  xlii.  p.  115. 


Variation  and  Natural  Selection.  89 

sidered  at  some  length  because,  on  the  hypothesis  of 
natural  selection,  they  admirably  illustrate  the  results 
which  may  be  reached  through  long-continued  elimination 
by  enemies. 

Sufficient  has  now  been  said  to  show  that  this  form  of 
elimination  is  an  important  factor.  We  are  not  at  present 
considering  the  question  how  variations  arise,  or  why  they 
should  take  any  particular  direction.  But  granting  the 
fact  that  variations  may  and  do  occur  in  all  parts  of  the 
organism,  it  is  clear  that,  in  a  group  of  organisms  sur- 
rounded by  enemies,  those  individuals  which  varied  in  the 
direction  of  swiftness,  cunning,  inconspicuousness,*  or  re- 
semblance to  protected  forms,  would,  other  things  being 
equal,  stand  a  better  chance  of  escaping  elimination. 

Elimination  by  competition  is,  as  Darwin  well  points 
out,  keenest  between  members  of  the  same  group  and 
among  individuals  of  the  same  species,  or  between  different 
groups  or  different  species  which  have,  so  to  speak,  similar 
aims  in  life.  While  enemies  of  various  kinds  are  preying 
upon  weaker  animals,  and  thus  causing  elimination  among 
them,  they  are  also  competing  one  with  another  for  the 
prey.  While  the  slower  and  stupider  organisms  are  suc- 
cumbing to  their  captors,  and  thus  leaving  more  active  and 
cunning  animals  in  possession  of  the  field,  the  slower  and 
stupider  captors,  failing  to  catch  their  cunning  and  active 
prey,  are  being  eliminated  by  competition.  While  protec- 
tive resemblance  aids  the  prey  to  escape  elimination  by 
enemies,  a  correlative  resemblance,  called  by  Mr.  Poulton 
aggressive  resemblance,  in  the  captors  aids  them  in  stealing 
upon  their  prey,  and  so  gives  advantage  in  competition. 
Thus  the  hunting  spider  closely  resembles  the  flies  upon 
which  he  pounces,  even  rubbing  his  head  with  his  fore  legs 
after  their  innocent  fashion. 

*  Since  the  above  was  written  and  sent  to  press,  there  has  been  added,  at 
the  Natural  History  Museum,  in  the  basement  hall,  a  case  illustrating  the 
adaptation  of  external  coleuring  to  the  conditions  of  life.  All  the  animals, 
birds,  etc.,  there  grouped  were  collected  in  the  Egyptian  desert,  whence  also 
the  rocks,  stones,  and  sand  on  which  they  are  placed  were  brought.  Though 
somewhat  crowded,  they  exemplify  protective  resemblance  very  well. 


90  Animal  Life  and  Intelligence. 

As  in  the  case  of  protective  resemblance,  so,  too,  in  its 
aggressive  correlative,  the  resemblance  may  be  general  or 
special,  or  may  reach  the  climax  of  mimicry.  And  since 
the  same  organism  is  not  only  a  would-be  captor,  but 
sometimes  an  unwilling  prey,  the  same  resemblance  may 
serve  to  protect  it  from  its  enemies  and  to  enable  it  to 
steal  upon  its  prey.  The  mantis,  for  example,  gains 
doubly  by  its  resemblance  to  the  vegetation  among  which 
it  lives.  Certain  spiders,  described  by  Mr.  H.  0.  Forbes,  in 
Java,  closely  resemble  birds'-droppings.  This  may  serve 
to  protect  them  from  elimination  by  birds;  but  it  also 
enables  them  to  capture  without  difficulty  unwary  butter- 
flies, which  are  often  attracted  by  such  excreta.  A  parasitic 
fly  (VoluceUa  bombylans)  closely  resembles  (Fig.  20)  a 
bumble-bee  (Bombus  muscorum),  and  is  thus  enabled  to  enter 
the  nest  of  the  bee  without  molestation.  Its  larvae  feed 
upon  the  larvae  of  the  bee.  The  cuckoo  bee  Psithyrus 
rupestris,  an  idle  quean,  who  collects  no  pollen,  and  has 
no  pollen-baskets,  steals  into  the  nest  of  the  bumble-bee 
Bombus  lapidarius,  and  lays  her  eggs  there.  The  re- 
semblance between  the  two  is  very  great,  and  it  not  only 
enables  the  mother  bee  to  enter  unmolested,  but  the 
young  bees,  when  they  are  hatched,  to  escape.  Another 
bee  (Nomada  solidaginis),  which  plays  the  cuckoo  on 
Halictus  cylindricus,  does  not  resemble  this  bee,  but  is 
wasp-like,  and  thus  escapes  molestation,  not  because  it 
escapes  notice,  but  because  it  looks  more  dangerous  than  it 
really  is.* 

Many  are  the  arts  by  which,  in  keen  competition, 
organisms  steal  a  march  upon  their  congeners — not,  be  it 
remembered,  through  any  conscious  adaptation,  but  through 
natural  selection  by  elimination.  Mr.  Poulton  describes 
an  Asiatic  lizard  (Phrynocephalus  mystaceus)  in  which  the 
"  general  surface  resembles  the  sand  on  which  it  is  found, 
while  the  fold  of  their  skin  at  each  angle  of  the  mouth  is 
of  a  red  colour,  and  is  produced  into  a  flower-like  shape 

*  I  have  to  thank  Mr.  H.  A.  Francis  for  drawing  my  attention  to  this, 
and  showing  me  the  insects  in  his  cabinet. 


Variation  and  Natural  Selection.  91 

exactly  resembling  a  little  red  flower  which  grows  in  the 
sand.  Insects,  attracted  by  what  they  believe  to  be  flowers, 
approach  the  mouth  of  the  lizard,  and  are,  of  course, 
captured."*  The  fishing  frog,  or  angler-fish,  is  possessed 
of  filaments  which  allure  small  fry,  who  think  them 
worms,  into  the  neighbourhood  of  the  great  mouth  in 
which  they  are  speedily  engulfed ;  and  certain  deep-sea 


Fig.  20.— Mimicry  of  bees  by  flies. 

a,  6,  Bombus  muscorum ;  c,  d,  Volucella  bombylans  ;  e,  Eristalis  tenax ;  f,  Apis  mellifica. 
The  underwings  of  the  hive  bee  (f)  were  invisible'in  the  photograph  from  which  the  figure  was 
drawn.  (From  an  exhibit  in  the  British  Natural  History  Museum.) 

forms  discovered  during  the  Challenger  expedition  have  the 
lure  illumined  by  phosphorescent  light. 

We  need  say  no  more  in  illustration  of  the  resem- 
blances which  have  enabled  certain  organisms  to  escape 
elimination  by  competition.  Once  more,  be  it  understood 

*  "  Colours  of  Animals,"  p.  73. 


92  Animal  Life  and  Intelligence. 

that  we  are  not  at  present  considering  how  any  of  these 
resemblances  have  been  brought  about ;  we  are  merely 
indicating  that,  given  certain  resemblances,  advantageous 
either  for  captor  or  prey,  those  organisms  which  possess 
them  not  will  have  to  suffer  elimination — elimination  by 
enemies,  or  else  elimination  by  competition. 

The  interaction  between  these  two  kinds  of  elimination 
is  of  great  importance.  Hunters  and  hunted  are  both,  so 
to  speak,  playing  the  game  of  life  to  the  best  of  their 
ability.  Those  who  fail  on  either  side  are  weeded  out ;  and 
elimination  is  carried  so  far  that  those  who  are  only  as 
good  as  their  ancestors  are  placed  at  a  disadvantage  as 
compared  with  their  improving  congeners.  The  standard 
of  efficiency  is  thus  improving  on  each  side ;  and  every 
improvement  on  the  one  side  entails  a  corresponding 
advance  on  the  other.  Nor  is  there  only  thus  a  competition 
for  subsistence,  and  arising  thereout  a  gradual  sharpening 
of  all  the  bodily  and  mental  powers  which  could  aid  in 
seeking  or  obtaining  food ;  there  is  also  in  some  cases  a 
competition  for  mates,  reaching  occasionally  the  climax  of 
elimination  by  battle.  There  is,  indeed,  competition  for 
everything  which  can  be  an  object  of  appetence  to  the  brute 
intelligence;  and,  owing  to  the  geometrical  tendency  in 
multiplication — the  law  of  increase — -the  competition  is 
keen  and  unceasing. 

Such,  then,  in  brief,  are  the  three  main  modes  of 
elimination :  elimination  by  physical  and  climatic  condi- 
tions ;  elimination  by  enemies ;  elimination  by  competition. 
Observe  that  it  is  a  differentiating  process.  Unlike  the 
indiscriminate  destruction  before  alluded  to,  the  incidence 
of  which  is  on  all  alike,  good,  bad,  and  indifferent,  it 
separates  the  well-adapted  from  the  ill-adapted,  dooming 
the  latter  to  death,  and  allowing  the  former  to  survive  and 
procreate  their  kind.  The  destruction  is  not  indiscriminate, 
but  differential. 

Let  us  now  turn  to  cases  of  selection,  properly  so  called, 
where  Nature  is  in  some  way  working  at  the  other  end  of 
the  scale  ;  where  her  method  is  not  the  elimination  of  the 


Variation  and  Natiiral  Selection.  93 

unfit,  but  the  selection  of  the  fit.  Such  a  case  may  be 
found  on  Darwin's  principles  in  brightly  coloured  flowers 
and  fruits.  "  Flowers,"  he  says,  "rank  amongst  the  most 
beautiful  productions  of  nature;  but  they  have  been 
rendered  conspicuous  in  contrast  with  the  green  leaves, 
and,  in  consequence,  at  the  same  time  beautiful,  so  that 
they  may  be  easily  observed  by  insects.  I  have  come  to 
this  conclusion  from  finding  it  an  invariable  rule  that, 
when  a  flower  is  fertilized  by  the  wind,  it  never  has  a  gaily 
coloured  corolla.  Several  plants  habitually  produce  two 
kinds  of  flowers — one  kind  open  and  coloured,  so  as  to 
attract  insects ;  the  other  closed,  not  coloured,  destitute  of 
nectar,  and  never  visited  by  insects.  Hence  we  may  con- 
clude that,  if  insects  had  not  been  developed  on  the  face  of 
the  earth,  our  plants  would  not  have  been  decked  with 
beautiful  flowers,  but  would  have  produced  only  such  poor 
flowers  as  we  see  on  our  fir,  oak,  nut,  and  ash  trees,  on 
grasses,  spinach,  docks,  and  nettles,  which  are  all  fertilized 
through  the  agency  of  the  wind.  A  similar  line  of  argu- 
ment holds  good  with  fruits  ;  that  a  ripe  strawberry  or 
cherry  is  as  pleasing  to  the  eye  as  to  the  palate ;  that  the 
gaily  coloured  fruit  of  the  spindle-wood  tree,  and  the  scarlet 
berries  of  the  holly,  are  beautiful  objects, — will  be  admitted 
by  every  one.  But  this  beauty  serves  merely  as  a  guide 
to  birds  and  beasts,  in  order  that  the  fruit  may  be  devoured 
and  manured  seeds  disseminated :  I  infer  that  this  is  the 
case  from  having  as  yet  found  no  exception  to  the  rule 
that  seeds  are  always  thus  disseminated  when  embedded 
within  a  fruit  of  any  kind  (that  is,  within  a  fleshy  or  pulpy 
envelope),  if  it  be  coloured  of  any  brilliant  tint,  or  rendered 
conspicuous  by  being  white  or  black."  * 

Here  we  have  a  case  of  the  converse  of  elimination — a 
case  of  genuine  selection  under  nature.  But  even  here  the 
process  of  elimination  also  comes  into  play,  for  the  visita- 
tions of  flowers  by  insects  involve  cross-fertilization.  The 
flowers  of  two  distinct  individuals  of  the  same  species  of 
plants  in  this  manner  fertilize  each  other ;  and  the  act  of 

*  "  Origin  of  Species,"  p.  161. 


94  Animal  Life  and  Intelligence. 

crossing,  as  Darwin  firmly  believed,  though  it  is  doubted 
by  some  observers  nowadays,  gives  rise  to  vigorous  seed- 
lings, which  consequently  would  have  the  best  chance  of 
flourishing  and  surviving — would  best  resist  elimination  by 
competition.  So  that  we  here  have  the  double  process  at 
work;  the  fairest  flowers  being  selected  by  insects,  and 
those  plants  which  failed  to  produce  such  flowers  being 
eliminated  as  the  relatively  unfit. 

If  we  turn  to  the  phenomena  of  what  Darwin  termed 
sexual  selection,  we  find  both  selection  and  elimination 
brought  into  play.  By  the  law  of  battle,  the  weaker  and 
less  courageous  males  are  eliminated  so  far  as  the  con- 
tinuation of  their  kind  is  concerned.  By  the  individual 
choice  of  the  females  (on  Darwin's  view,  by  no  means 
universally  accepted),  the  finer,  bolder,  handsomer,  and 
more  tuneful  wooers  are  selected. 

Let  us  again  hear  the  voice  of  Darwin  himself.  "  Most 
male  birds,"  he  says,  "are  highly  pugnacious  during  the 
breeding  season,  and  some  possess  weapons  especially 
adapted  for  fighting  with  their  rivals.  But  the  most 
pugnacious  and  the  best-armed  males  rarely  or  never 
depend  for  success  solely  on  their  power  to  drive  away  or 
kill  their  rivals,  but  have  special  means  for  charming  the 
female.  With  some  it  is  the  power  of  song,  or  of  emitting 
strange  cries,  or  of  producing  instrumental  music ;  and  the 
males  in  consequence  differ  from  the  females  in  their  vocal 
organs  or  in  the  structure  of  certain  feathers.  From  the 
curiously  diversified  means  for  producing  various  sounds, 
we  gain  a  high  idea  of  the  importance  of  this  means  of 
courtship.  Many  birds  endeavour  to  charm  the  females 
by  love-dances  or  antics,  performed  on  the  ground  or  in 
the  air,  and  sometimes  at  prepared  places.  But  ornaments 
of  many  kinds,  the  most  brilliant  tints,  combs  and  wattles, 
beautiful  plumes,  elongated  feathers,  top-knots,  and  so 
forth,  are  by  far  the  commonest  means.  In  some  cases, 
mere  novelty  appears  to  have  acted  as  a  charm.  The 
ornaments  of  the  males  must  be  highly  important  to  them, 
for  they  have  been  acquired  in  not  a  few  cases  at  the  cost 


Variation  and  Natural  Selection.  95 

of  increased  danger  from  enemies,  and  even  at  some  loss 
of  power  in  fighting  with  their  rivals.*  .  .  .  What,  then, 
are  we  to  conclude  from  these,  facts  and  considera- 
tions? Does  the  male  parade  his  charms  with  so  much 
pomp  and  rivalry  for  no  purpose?  Are  we  not  justified 
in  believing  that  the  female  exerts  a  choice,  and  that 
she  receives  the  addresses  of  the  male  who  pleases  her 
most  ?  "  f 

Here  again,  then,  we  have  the  combined  action  of  elimi- 
nation and  selection.  And  now  we  may  note  that  selec- 
tion involves  intelligence — involves  the  play  of  appetence 
and  choice.  Hence  it  is  that,  when  we  come  to  consider 
the  evolution  of  human-folk,  the  principle  of  elimination  is 
so  profoundly  modified  by  the  principle  of  selection.  Not 
only  are  the  weaker  eliminated  by  the  inexorable  pressure 
of  competition,  but  we  select  the  more  fortunate  individuals 
and  heap  upon  them  our  favours.  This  enables  us  also  to 
soften  the  rigour  of  the  blinder  law ;  to  let  the  full  stress 
of  competitive  elimination  fall  upon  the  worthless,  the  idle, 

^          the  profligate,  and  the  vicious ;  but  to  lighten  its  incidence 

^          on  the  deserving  but  unfortunate. 

*  Both  selection  and  elimination  occurring  under  nature, 

\^\  but  elimination  having  by  far  the  wider  scope,  we  may  now 
inquire  what  will  be  their  effect  as  regards  the  three  modes 
of  variation — advantageous,  disadvantageous,  and  neutral. 
It  must  be  remembered  that  these  modes  are  relative  and 
dependent  upon  circumstances,  so  that  variations,  neutral 
under  certain  conditions,  may  become  relatively  disadvan- 
tageous under  other  conditions.  Selection  clearly  leads  to 
the  preservation  of  advantageous  variations  alone,  and 
these  variations  are  advantageous  in  so  far  as  they  meet 
the  taste  of  the  selecting  organism.  For  selection  depends 
upon  individual  choice;  and  uniformity  of  selection  is 
entirely  dependent  upon  uniformity  in  the  standard  of 
taste.  If,  as  Darwin  contends,  the  splendid  plumage  and 
tuneful  notes  of  male  birds  are  the  result  of  a  selection  of 
mates  by  the  hens,  there  must  be  a  remarkable  uniformity 
*  "Descent  of  Man,"  summary  of  chap.  xvi.  pt.  ii.  t  Ibid.  chap.  xiv. 


96  Animal  Life  and  Intelligence. 

of  taste  among  the  hens  of  each  particular  species,  since 
there  is  a  uniformity  of  coloration  among  the  cock-birds. 
It  may  be  said  that  in  all  their  mental  endowments  there 
is  greater  uniformity  among  animals  than  among  men ;  and 
it  is  true  that  individuation  has  not  been  carried  so  far  in 
them  as  in  human-folk.  Still,  careful  observers  of  animals 
see  in  them  many  signs  of  individual  character ;  and  this 
uniformity  in  the  standard  of  taste  in  each  species  of 
birds  seems  to  many  naturalists  a  real  difficulty  in  the 
way  of  the  acceptance  of  sexual  selection.  We  shall, 
however,  return  to  this  point.  For  the  present  it  is 
clear  that  selection  chooses  out  advantageous  variations, 
that  the  advantage  is  determined  by  the  taste  of  the 
selector,  and  that  uniform  selection  implies  uniformity  of 
taste. 

Turning  to  elimination,  it  is  clear  that  it  begins  by 
weeding  out,  first  the  more  disadvantageous,  then  the  less 
disadvantageous  variations.  It  leaves  both  the  advan- 
tageous and  the  neutral  in  possession  of  the  field.  I 
imagine  that  many,  perhaps  most,  of  the  variations 
tabulated  by  Mr.  Wallace  and  other  observers  belong  to 
the  neutral  category.  Their  fluctuating  character  seems 
to  indicate  that  this  is  so.  In  any  case,  they  are 
variations  which  have  so  far  escaped  elimination.  And 
I  think  they  are  of  great  and  insufficiently  recognized 
importance.  They  permit,  through  interbreeding,  of  end- 
less experiments  in  the  combination  of  variations,  some  of 
which  cannot  fail  to  give  favourable  results. 

It  is  just  possible  that  it  may  be  asked — If  in  natural 
elimination  there  is  nothing  more  than  the  weeding  out 
of  the  unfit  and  the  suppression  of  disadvantageous  varia- 
tions, where  is  the  possibility  of  advance  ?  The  standard 
may  thus  be  maintained,  but  where  is  the  possibility  of 
progress  ?  Such  an  objection  would,  however,  imply  forget- 
fulness  of  the  fact  that  all  the  favourable  variations  remain 
to  leaven  the  residual  lump.  Given  a  mean,  with  plus  and 
minus  variations :  if  in  any  generations  the  minus  varia- 
tions are  got  rid  of,  the  mixture  of  the  mean  with  the  plus 


Variation  and  Natural  Selection.  97 

variations  will  give  a  new  mean  nearer  the  plus  or  advan- 
tageous end  of  the  scale  than  the  old  mean.  By  how 
much  the  favourable  variations  tend  to  raise  the  mean 
standard,  by  so  much  will  the  race  tend  to  advance. 
But  in  this  process  I  see  no  reason  why  the  neutral 
variations  should  be  eliminated,  except  in  so  far  as,  in 
the  keen  struggle  for  existence,  they  become  relatively 
unfavourable. 

It  is  clear,  however,  that  the  intercrossing  and  inter- 
breeding which  occurs  between  average  individuals  on  the 
one  hand,  and  those  possessing  favourable  variations  on 
the  other,  while  it  tends  gradually  to  raise  the  mean 
standard,  tends  also  at  the  same  time  to  reduce  the  advan- 
tageous variations  towards  the  mean.  It  must  tend  to  check 
advance  by  leaps  and  bounds,  and  to  justify  the  adage, 
Natura  nil  fatit  per  saltum.  At  the  same  time,  it  will 
probably  have  a  greater  tendency  to  reduce  to  a  mean  level 
neutral  variations  indefinite  in  direction  than  advantageous 
variations  definite  in  direction.  Still,  it  is  a  most  im- 
portant factor,  and  one  not  to  be  neglected.  It  tends  to 
uniformity  in  the  species,  and  checks  individualism.  It 
may  act  as  a  salutary  brake  on  what  we  may  figuratively 
term  hasty  and  ill-advised  attempts  at  progress.  And  at 
the  same  time,  it  favours  repeated  new  experiments  in  the 
combination  of  variations,  occasionally,  we  may  suppose, 
with  happy  results. 

But  it  does  more  than  this.     It  tends  to  check,  and,  if) 
the  offspring  always  possessed  the  blended  character  of  bothf 
parents,  would  be  absolutely  fatal  to,  divergence  of  character  \ 
within  the  interbreeding  members  of  a  species.     And  yet  1 
no  fact  is  more  striking  than  this  divergence  of  character.' 
It  is  seen  in  the  diversified  products  of  human  selection  ; 
for  example,  among  pigeons.     It  is  seen  in  the  freedom  of 
nature.     Mr.    Wallace   gives   many   examples.     "  Among 
our  native  species,"  he  says,  "we  see  it  well  marked  in  the 
different  species  of  titmice,  pipits,  and  chats.     The  great 
titmouse,  by  its  larger  size  and  stronger  bill,  is  adapted  to 
feed  on  larger  insects,  and  is  even  said  sometimes  to  kifl 

H 


98  Animal  Life  and  Intelligence. 

small  and  weak  birds.  The  smaller  and  weaker  coal-tit- 
mouse has  adopted  a  more  vegetarian  diet,  eating  seeds  as 
well  as  insects,  and  feeding  on  the  ground  as  well  as  among 
trees.  The  delicate  little  blue  titmouse,  with  its  very  small 
bill,  feeds  on  the  minutest  insects  and  grubs,  which  it 
extracts  from  crevices  of  bark  and  from  the  buds  of  fruit 
trees.  The  marsh-titmouse,  again,  has  received  its  name 
from  the  low  and  marshy  localities  it  frequents ;  while  the 
crested  titmouse  is  a  Northern  bird,  frequenting  especially 
pine  forests,  on  the  seeds  of  which  trees  it  partially  feeds. 
Then,  again,  our  three  common  pipits — the  tree-pipit,  the 
meadow-pipit,  and  the  rock-pipit,  or  sea-lark — have  each 
occupied  a  distinct  place  in  nature,  to  which  they  have 
become  specially  adapted,  as  indicated  by  the  different 
form  and  size  of  the  hind  toe  and  claw  in  each  species. 
So  the  stone-chat,  the  whin-chat,  and  the  wheat-ear  are  all 
slightly  divergent  forms  of  one  type,  with  modifications  in 
the  shape  of  the  wing,  feet,  and  bill  adapting  them  to 
slightly  different  modes  of  life."  *  There  is  scarcely  a 
genus  that  does  not  afford  examples  of  divergent  species. 
The  question  then  naturally  occurs — How  have  these 
divergent  forms  escaped  the  swamping  effects  of  inter- 
crossing ? 

That  perfectly  free  intercrossing,  between  any  or  all  of 
the  individuals  of  a  given  group  of  animals,  is,  so  long  as 
the  characters  of  the  parents  are  blended  in  the  offspring, 
fatal  to  divergence  of  character,  is  undeniable.  Through 
the  elimination  of  less  favourable  variations,  the  swiftness, 
strength,  and  cunning  of  a  race  may  be  gradually  improved. 
But  no  form  of  elimination  can  possibly  differentiate  the 
group  into  swift,  strong,  and  cunning  varieties,  distinct 
from  each  other,  so  long  as  all  three  varieties  freely  inter- 
breed, and  the  characters  of  the  parents  blend  in  the  off- 
spring. Elimination  may  and  does  give  rise  to  progress  in 
any  given  group  as  a  group ;  it  does  not  and  cannot  give 
rise  to  differentiation  and  divergence,  so  long  as  interbreed- 
ing with  consequent  interblending  of  characters  be  freely 

*  "  Darwinism,"  p.  108. 


Variation  and  Natural  Selection.  99 

permitted.  Whence  it  inevitably  follows,  as  a  matter  of 
simple  logic,  that  where  divergence  has  occurred,  inter- 
crossing and  interblending  must  in  some  way  have  been 
lessened  or  prevented. 

Thus  a  new  factor  is  introduced,  that  of  isolation,  or 
segregation.  And  there  is  no  questioning  the  fact  that  it  is 
of  great  importance.*  Its  importance  can,  indeed,  only  be 
denied  by  denying  the  swamping  effects  of  intercrossing, 
and  such  denial  implies  the  tacit  assumption  that  inter- 
breeding and  interblending  are  held  in  check  by  some  form 
of  segregation.  The  isolation  explicitly  denied  is  implicitly 
assumed. 

There  are  several  ways  in  which  isolation,  or  segregation, 
may  be  effected.  Isolation  by  geographical  barriers  is  the 
most  obvious.  A  stretch  of  water,  a  mountain  ridge,  a 
strip  of  desert  land,  may  completely,  or  to  a  large  extent, 
prevent  any  intercrossing  between  members  of  a  species  on 
either  side  of  the  barrier.  The  animals  which  inhabit  the 
several  islands  of  the  Galapagos  Archipelago  are  closely 
allied,  but  each  island  has  its  particular  species  or  well- 
marked  varieties.  Intercrossing  between  the  several 
varieties  on  the  different  islands  is  prevented,  and  diver- 
gence is  thus  rendered  possible  and  proceeds  unchecked. 
It  is  said  that  in  the  Zuyder  Zee  a  new  variety  of  herrings, 
the  fry  of  which  are  very  small  compared  with  open-sea 
herrings,  is  being  developed.  And  the  salmon  introduced 
into  Tasmania  seem  to  be  developing  a  fresh  variety 
with  spots  on  the  dorsal  fin  and  a  tinge  of  yellow  on  the 
adipose  fin.  In  the  wooded  valleys  of  the  Sandwich  Islands 
there  are  allied  but  distinct  species  of  land-shells.  The 
valleys  that  are  nearest  each  other  furnish  the  most  nearly 
related  forms,  and  the  degree  of  divergence  is  roughly 
measured  by  the  number  of  miles  by  which  they  are 
separated.  Here  there  is  little  or  no  intercrossing  between 

*  Its  importance  in  artificial  selection  was  emphasized  by  Darwin :  "  The 
prevention  of  free  crossing,  and  the  intentional  matching  of  individual  animals, 
are  the  corner-stones  of  the  breeder's  art "("  Animals  and  Plants  under 
Domestication,"  ii.  62). 


ioo  Animal  Life  and  Intelligence. 

the  slow-moving  molluscs  in  adjoining  valleys ;  none  at  all 
between  those  at  any  distance  apart. 

But  even  if  there  are  no  well-marked  physical  barriers, 
the  members  of  a  species  on  a  continent  or  large  island 
tend  to  fall  into  local  groups,  between  which,  unless  the 
animal  be  of  a  widely  ranging  habit,  there  will  be  little 
intercrossing.  Hence  local  varieties  are  apt  to  occur,  and 
varieties  show  the  first  beginnings  of  that  divergence  which, 
if  carried  further  and  more  deeply  ingrained,  results  in  the 
differentiation  of  species.  Geographically,  therefore,  we 
may  have  either  complete  isolation  or  local  segregation, 
and  in  both  cases  the  possibility  of  divergence. 

Another  mode  of  segregation  arises  also  out  of 
geographical  conditions.  If  variations  of  habits  occur 
(and  structure  is  closely  correlated  with  habit)  such  that 
certain  individuals  take  to  the  mountains,  others  to  the 
plains  or  valleys ;  or  that  certain  individuals  take  to  the 
forests,  others  to  the  open  country;  the  probabilities  are 
that  the  forest  forms  will  interbreed  frequently  with  each 
other,  but  seldom  with  those  in  the  open,  and  so  with  the 
other  varieties.  The  conditions  of  forest  life  or  mountain 
life  being  thus  similar  throughout  a  large  area,  and  life 
being  through  elimination  slowly  but  surely  adapted  to  its 
environment,  there  might  thus  arise  two  distinct  varieties 
scattered  throughout  the  length  and  breadth  of  the  area, 
the  one  inhabiting  the  mountains,  the  other  the  forests. 
In  illustration  of  this  mode  of  segregation,  we  may  take 
the  case  of  two  species  of  rats  which  have  recently  been 
found  by  Mr.  C.  M.  Woodford  on  one  of  the  Solomon 
Islands.  These  two  quite  distinct  species  are  regarded  by 
Mr.  Oldfield  Thomas  as  slightly  modified  descendants  of 
one  parent  species,  the  modifications  resulting  from  the 
fact  that  of  this  original  species  some  individuals  have 
adopted  a  terrestrial,  others  an  arboreal  life,  and  their 
respective  descendants  have  been  modified  accordingly. 
Thus  Mus  rex  lives  in  trees,  has  broad  foot-pads,  and  a 
long  rasp-like,  probably  semi-prehensile,  tail ;  while  Mus 
imperator  lives  on  the  ground,  has  smaller  pads,  and  a 


Variation  and  Natural  Selection.  101 

short,  smooth  tail.  The  segregation  of  these  two  species 
has  probably  been  effected  by  the  difference  of  their  mode 
of  life,  and  each  has  been  adapted  to  its  special  environment 
through  the  elimination  of  those  individuals  which  were 
not  in  harmony  with  the  condition  of  their  life.  It  is 
probable  that  this  mode  of  segregation  has  been  an  im- 
portant one.  And  it  is  clear  that  in  many  cases  competition 
would  be  a  co-operating  factor  in  this  process,  weaker 
organisms  being  forced  into  otherwise  uncongenial  habitats 
through  the  stress  of  competitive  elimination,  the  weaker 
forms  not  perishing,  but  being  eliminated  from  more 
favoured  areas. 

Protective  coloration  may  also  be  a  means  of  segrega- 
tion. A  species  of  insects  having  no  protective  resemblance 
might  vary  in  two  directions — in  the  direction  of  green 
tints,  assimilating  their  hue  to  that  of  vegetation ;  and  in 
the  direction  of  sandy  or  dull  earthy  colours,  assimilating 
them  to  the  colour  of  the  soil.  In  the  one  variety  elimina- 
tion would  weed  out  all  but  the  green  forms,  and  these 
would  be  left  to  intercross.  In  the  other  variety,  green 
forms  would  be  eliminated,  dull-brown  forms  being  left  to 
interbreed.  Stragglers  from  one  group  into  the  other 
would  stand  a  chance  of  elimination  before  interbreeding 
was  effected.* 

In  the  case  of  birds  whose  freedom  of  flight  gives  them 
a  wide  range,  sometimes  almost  a  world-wide  range,  it 
would  seem  at  first  sight  that  their  facilities  for  inter- 
breeding and  intercrossing  are  so  great  that  divergence  is 
well-nigh  impossible.  And  yet  the  examples  of  divergence  I 
cited  from  Mr.  Wallace  were  taken  from  birds,  and  it  is  well 
known  that  divergence  is  particularly  well  shown  in  this 
class.  But  when  the  habits  of  birds  are  studied  attentively, 
it  is  found  that,  wide  as  is  their  range,  their  breeding  area 
is  often  markedly  restricted.  The  sanderling  and  knot 

*  From  the  absence  of  interblending  in  some  cases  (to  be  considered 
shortly),  both  brown  and  green  forms  may  be  produced ;  and  under  certain 
circumstances,  even  a  power  of  becoming  either  brown  or  green  in  the 
presence  of  appropriate  stimuli. 


102  Animal  Life  and  Intelligence. 

range  freely  during  the  winter  throughout  the  Northern 
hemisphere;  but  their  breeding  area  is  restricted  to 
the  north  polar  region.  The  interbreeding  within  this 
area  keeps  the  species  one  and  homogeneous,  notwith- 
standing its  wide  range,  and,  at  the  same  time,  prevents 
intercrossing  with  allied  species  with  different  breeding- 
grounds. 

Another  most  important  mode  of  segregation  among 
animals  arises  out  of  habitual  or  instinctive  preferences. 
Where  varieties  are  formed  there  is  a  tendency  for  like  to 
breed  with  like.  In  the  Falkland  Islands  the  differently 
coloured  herds  of  cattle,  all  descended  from  the  same  stock, 
keep  separate,  and  interbreed  with  each  other,  but  not  with 
individuals  outside  their  own  colour-caste.  If  two  flocks 
of  merino  sheep  and  heath  sheep  be  mixed  together,  they 
do  not  interbreed.  In  the  Forest  of  Dean  and  in  the  New 
Forest,  the  dark  and  pale  coloured  herds  of  fallow  deer 
have  never  been  known  to  intermingle.*  Here  we  have  a 
case  of  selective  segregation  through  preferential  mating,  and 
may  find  therein  the  basis  of  sexual  selection  in  its  higher 
ranges  as  advocated  by  Darwin. 

The  question  of  sexual  selection  will,  however,  be  briefly 
considered  in  the  chapter  on  "Organic  Evolution."  At 
present  what  we  have  to  notice  is  that,  through  preferential 
mating,  segregation  is  effected.  The  forms  that  interbreed 
have  a  distinguishing  colour.  From  this  it  is  but  a  step 
to  the  possession,  not  merely  of  a  distinguishing  colour, 
but  of  distinguishing  colour-markings.  Hence,  through 
preferential  mating,  may  arise  those  special  markings 
which  so  frequently  distinguish  allied  species.  They  not 
only  enable  us  to  recognize  species  as  distinct,  but  enable 
the  species  which  possess  them  to  recognize  the  members 
of  their  own  kind.  Mr.  Wallace  calls  these  diacritical 
marks  recognition-marks,  and  gives  many  illustrative 
examples. f  They  are  especially  noticeable  in  gregarious 
animals  and  in  birds  which  congregate  in  flocks  or  which 

*  Wallace,  "  Darwinism,"  p.  172,  where  other  examples  are  cited, 
t  Ibid.  pp.  217,  at  seq. 


Variation  and  Natural  Selection.  103 

migrate  together.  Mr.  Wallace  considers  that  they  "  have 
in  all  probability  been  acquired  in  the  process  of  differentia- 
tion for  the  purpose  of  checking  the  intercrossing  of  allied 
forms  ;  "  for  "  one  of  the  first  needs  of  a  new  species  would 
be  to  keep  separate  from  its  nearest  allies,  and  this  could 
be  more  readily  done  by  some  easily  seen  external  mark 
of  difference."  This  language  seems,  however,  to  savour 
of  teleology  (that  pitfall  of  the  evolutionist).  The  cart  is 
placed  before  the  horse.  The  recognition-marks  were,  I 
believe,  not  produced  to  prevent  intercrossing,  but  inter- 
crossing has  been  prevented  because  of  preferential  mating 
between  individuals  possessing  special  recognition-marks. 
To  miss  this  point  is  to  miss  an  important  segregation- 
factor.  Undoubtedly,  other  tendencies  co-operate  in  main- 
taining the  standard  of  the  recognition-marks.  Stragglers 
who  failed  in  the  matter  of  recognition  would  get  separated 
from  their  fellows,  and  stand  a  greater  chance  of  elimi- 
nation by  enemies ;  young  who  failed  in  this  respect  would 
be  in  like  condemnation.  Still,  I  cannot  doubt  that  the 
foundations  of  recognition-marks  were  laid  in  preferential 
mating,  and  that  in  this  we  have  an  important  factor  in 
segregation. 

We  may  here  note,  in  passing,  as  also  arising  out  of 
preference,  how  the  selection  of  flowers  by  insects  may 
lead  to  segregation ;  for  insects  seem  often  to  have  habitual 
or  instinctive  colour-preferences.  Flowers  of  similar  colour 
would  be  thus  cross-fertilized,  but  would  not  intercross  with 
those  of  different  colour,  whence  colour-varieties  might 
arise.  It  is  important  to  note  that  in  these  cases  there  is 
a  psychological  factor  in  evolution. 

We  have  so  far  assumed  that  intercrossing  of  parents 
and  interblending  of  their  characters  in  the  offspring 
always  go  together.  This,  we  must  now  notice,  is  not 
always  the  fact.  If  a  blue-eyed  Saxon  marry  a  dark-eyed 
Italian,  the  children  will  have  blue  eyes  or  dark  eyes,  not 
eyes  of  an  intermediate  tint.  The  characters  do  not  inter- 
blend.  The  ancon,  or  otter-sheep,  a  breed  with  a  long 
body  and  short,  bandy  legs,  appeared  in  Massachusetts  as 


IO4  Animal  Life  and  Intelligence. 

a  chance  sport  in  a  single  lamb.  The  offspring  of  this 
ram  were  either  ancons  or  ordinary  sheep.  The  ancon 
characters  did  not  blend.  Hence  for  a  time  a  definite 
breed  was  maintained.  We  may  call  this  mode  of  isola- 
tion isolation  by  exclusive  inheritance. 

A  further  mode  of  isolation  or  segregation,  for  which 
Mr.  Eomanes*  claims  a  foremost,  indeed,  the  foremost, 
place,  is  physiological  isolation  as  due  to  differential  fertility. 
One  among  the  many  variations  to  which  organisms  are 
subject  is  a  variation  in  fertility,  which  may  reach  the 
climax  of  absolute  sterility.  But  it  is  clear  that  a  sterile 
variation  carries  with  it  its  own  death-warrant,  since  the 
sterile  individual  leaves  no  descendants  to  inherit  its  pecu- 
liarity. Eelative  infertility,  too,  unless  it  chances  to  be 
correlated  with  some  unusual  excellence,  would  be  no 
advantage,  would  be  transmitted  to  few  descendants,  and 
would  tend  to  be  extinguished.  The  same  is  not  true, 
however,  of  differential  fertility.  "It  is  by  no  means 
rare,"  said  Darwin,  f  "to  find  certain  males  and  females 
which  will  not  breed  together,  though  both  are  known  to 
be  perfectly  fertile  with  other  males  and  females."  Mr. 
Eomanes  assumes,  as  a  starting-point,  the  converse  of 
this,  namely,  that  certain  males  and  females  will  breed  to- 
gether, though  they  are  infertile  with  all  other  members 
of  the  species. 

Suppose,  then,  a  variety  to  arise  which  is  perfectly 
fertile  within  the  limits  of  the  varietal  form,  but  im- 
perfectly fertile  or  infertile  with  the  parent  species. 
Such  a  variety  would  have  to  run  the  risks  of  those  ill 
effects  which,  as  Darwin  showed,}:  are  attendant  upon  close 
interbreeding.  But  Mr.  Wallace  points  out§  that  these 
ill  effects  may  not  be  so  marked  under  nature  as  they  are 
under  domestication.  Suppose,  then,  that  it  escapes  these 
ill  effects.  In  this  case,  Mr.  Eomanes  urges,  it  would 
neither  be  swamped  by  intercrossing  nor  die  out  on 

*  Journal  of  the  Linnaean  Society,  vol.  xix.  No.  115  :  "  Zoology." 
t  "  Animals  and  Plants  under  Domestication,"  p.  145. 
J  Ibid.  chap.  xvii.  §  "  Darwinism,"  p.  326. 


Variation  and  Natural  Selection.  105 

account  of  sterility.  But  although  it  could  not  be  swamped 
by  intercrossing,  still,  if  it  arose  sporadically,  here  a  case, 
there  a  case,  and  so  on,  the  chances  would  be  enormously 
against  the  perpetuation  of  the  variety,  unless  some  co- 
operating mode  of  segregation  aided  in  bringing  together 
the  varying  individuals.  If,  for  example,  there  were  a 
segregation  of  these  variants  in  a  particular  habitat — all 
the  variants  meeting  in  some  definite  locality  for  breeding 
purposes ;  or  if  there  were  a  further  segregation  through 
mutual  preferences;  or  if,  again,  there  were  a  further 
segregation  in  time ;  the  variety  might  obtain  a  firm 
footing.  But  without  these  co-operating  factors  it  is  clear 
that  if  one  male  and  one  female  in  a  hundred  individuals 
varied  in  this  particular  way,  the  chances  would  be  at 
least  forty- nine  to  one  against  their  happening  to  mate 
together. 

It  is  interesting  to  note  that  almost  the  only  particular 
example  given  by  Mr.  Eomanes  in  illustration  of  his  theory 
is  one  that  involves  the  co-operation  of  one  of  these  further 
segregation-factors.  Suppose,  he  says,  the  variation  in 
the  reproductive  system  is  such  that  the  season  of  flower- 
ing or  of  pairing  becomes  either  advanced  or  retarded. 
This  particular  variation  being  inherited,  the  variety  breed- 
ing, let  us  say,  in  May,  the  parent  species  in  July,  there 
would  arise  two  races,  each  perfectly  fertile  within  its  own 
limits,  but  incapable  of  crossing  with  the  other.  Thus  is 
constituted  "a  barrier  to  intercrossing  quite  as  effectual 
as  a  thousand  miles  of  ocean."  Yes  !  a  time-barrier  instead 
of  a  space-barrier.  The  illustration  is  faulty,  inasmuch  as 
it  introduces  a  mode  of  segregation  other  than  that  in 
question.  I  think  it  very  improbable  that  differential 
fertility  alone,  without  the  co-operation  of  other  segregation- 
factors,  would  give  rise  to  separate  varieties  capable  of 
maintaining  themselves  as  distinct  species. 

That  distinct  species  are  generally  mutually  infertile, 
or  more  frequently  still,  that  their  male  offspring  are 
sterile,  is,  however,  an  undoubted  fact.  But  there  are, 
exceptions.  Fertile  hybrids  between  the  sheep  and  the 


io6  Animal  Life  and  Intelligence. 

goat  seem  to  be  well  authenticated.  Of  rats  Darwin 
says  that  "in  some  parts  of  London,  especially  near 
the  docks,  \vhere  fresh  rats  are  frequently  imported,  an 
endless  variety  of  intermediate  forms  may  be  found 
between  the  brown,  black,  and  snake  rat,  which  are  all 
three  usually  ranked  as  distinct  species."  *  Fertile  hybrids 
have  been  produced  between  the  green-tinted  Japanese  and 
the  long-tailed  Chinese  pheasants.  Mr.  Thomas  Moore, 
of  Fareham,  in  Hants,  has  been  particularly  successful  in 
producing  a  hybrid  breed  between  the  golden  pheasant 
(Thaumalia  picta),  whose  habitat  is  Southern  and  South- 
eastern China,  and  the  Amherst  pheasant  (Thaumalia 
amherstitz),  which  is  found  in  the  mountains  of  Yunnan 
and  Thibet.  In  answer  to  my  inquiries,  Mr.  Moore  kindly 
informs  me  that  he  "has  bred  the  half-bred  gold  and 
Amherst  pheasant,  crossed  them  again  with  gold,  anjl  re- 
crossed  them  with  half-bred  Amherst,  and  kept  on  crossing 
until  only  a  strain  of  the  gold  pheasant  remained.  The 
result  is  that  the  birds  so  produced  are  far  handsomer  than 
either  breed,  since  the  feathers  composing  their  tiplets  as 
well  as  those  under  the  chin  are  of  so  beautiful  a  colour 
that  they  beggar  description.  They  all  breed  most  freely, 
and  are  much  more  vigorous  than  the  pure  gold  or  Amherst, 
and  their  tails  reach  a  length  of  over  three  feet.  They  are 
also  exceedingly  prolific.  Out  of  a  batch  of  forty-two  eggs, 
forty  chickens  were  hatched  out,  of  which  thirty-seven  were 
reared  to  perfection." 

Still,  though  there  are  exceptions,  the  general  infertility 
of  allied  species  when  crossed  is  a  fact  in  strong  contrast 
with  the  marked  fertility  of  varieties  under  domestication  ; 
concerning  which,  however,  it  should  be  noted  that  our 
domesticated  animals  have  been  selected  to  a  very  large 
extent  on  account  of  the  freedom  with  which  they  breed 
in  confinement,  and  that  domestication  has  probably  a 
tendency  to  increase  fertility.  The  question,  therefore, 
arises — Is  the  infertility  between  species,  and  the  general 

*  "  Animals  and  Plants  under  Domestication,"  vol.  ii.  p.  65.     For  Darwin's 
general  conclusions  on  hybridism,  see  vol.  ii.  p.  162  of  the  same  work. 


Variation  and  Natural  Selection.  107 

sterility  of  their  male  offspring,  a  secondary  effect  of  their 
segregation?  or  is  their  segregation  the  direct  effect  of 
their  differential  fertility?  The  former  is  the  general 
opinion  ;  the  latter  is  held  by  Mr.  Eomanes.  He  contends 
that  sterility  is  the  primary  distinction  of  species,  other 
specific  characters  being  secondary,  and  regards  it  as  a  pure 
assumption  to  say  that  the  secondary  differences  between 
species  have  been  historically  prior  to  the  primary  differ- 
ence. I  do  not  propose  to  discuss  this  question.  While  it 
seems  to  me  in  the  highest  degree  improbable  that 
differential  fertility,  apart  from  other  co-operating  factors, 
has  been  or  could  be  a  practical  mode  of  segregation,  it 
has  probably  been  a  not  unimportant  factor  in  association 
with  other  modes  of  segregation  or  isolation.  Suppose,  for 
example,  two  divergent  local  varieties  were  to  arise  in 
adjacent  areas,  and  were  subsequently  (by  stress  of  com- 
petition or  by  geographical  changes)  driven  together  into 
a  single  area :  we  are  justified  in  believing,  from  the 
analogy  of  the  Falkland  Island  cattle,  the  Forest  of  Dean 
deer,  and  other  similar  observed  habits,  that  preferential 
breeding,  kind  with  kind,  would  tend  to  keep  them  apart. 
But,  setting  this  on  one  side,  let  us  say  they  interbreed. 
If,  then,  their  unions  are  fertile,  the  isolation  will  be 
annulled  by  intercrossing — the  two  varieties  will  form  one 
mean  or  average  variety.  But  if  the  unions  be  infertile, 
the  isolation  will  be  preserved,  and  the  two  varieties  will 
continue  separate.  Suppose  now,  and  the  supposition  is 
by  no  means  an  improbable  one,  that  this  has  taken  place 
again  and  again  in  the  evolution  of  species :  then  it  is 
clear  that  those  varietal  forms  which  had  continued  to  be 
fertile  together  would  be  swamped  by  intercrossing  ;  while 
those  varietal  forms  which  had  become  infertile  would 
remain  isolated.  Hence,  in  the  long  run,  isolated  forms 
occupying  a  common  area  would  be  infertile.  Or  suppose, 
once  more,  that,  instead  of  the  unions  between  the  two 
varietal  forms  being  infertile,  they  are  fertile,  but  give  rise 
to  sterile  (mule)  or  degenerate  offspring,  as  is  said  to  be 
the  case  in  the  unions  of  Japanese  and  Ainos  :  then  it  is 


io8  Animal  Life  and  Intelligence. 

clear  that  the  sterile  or  degenerate  offspring  of  such  unions 
would  be  eliminated,  and  intercrossing,  even  though  it 
occurred,  would  be  inoperative  while  breeding  within  the 
limits  of  the  variety  continued  unchecked. 

Sufficient  has  now  been  said  concerning  the  modes  of 
isolation  and  segregation,  geographical,  preferential,  and 
physiological.  We  must  now  consider  their  effects.  Where 
the  isolated  varieties  are  under  different  conditions  of  life, 
there  will  be,  through  the  elimination  of  the  ill-adapted  in 
each  case,  differential  adaption  to  these  different  conditions. 
But  suppose  the  conditions  are  similar :  can  there  be 
divergence  in  this  case  ?  The  supposition  is  a  highly 
hypothetical  one,  because  it  postulates  that  all  the  con- 
ditions, climatal,  environmental,  and  competitive,  are  alike, 
which  would  seldom,  if  ever,  be  likely  to  occur.  Let  us, 
however,  make  the  supposition.  Let  us  suppose  that  an 
island  is  divided  into  two  equal  halves  by  the  submersion 
of  a  stretch  of  lowland  running  across  it.  Then  the  only 
possible  causes  of  divergence  would  lie  in  the  organisms 
themselves  *  thus  divided  into  two  equal  groups.  We  have 
seen  that  variations  may  be  advantageous,  disadvantageous, 
or  neutral.  The  neutral  form  a  fluctuating,  unfixed, 
indefinite  body.  But  they  afford  the  material  with  which 
nature  may  make,  through  intercrossing,  endless  experi- 
ments in  new  combinations,  some  of  which  may  be  profit- 
able. Such  profitable  variations  would  escape  elimination, 
and,  if  not  bred  out  by  intercrossing,  would  be  preserved. 
In  any  case,  the  variety  would  tend  to  advance  through 
elimination  as  previously-indicated.  But  in  the  two  equal 
groups  we  are  supposing  to  have  become  geographically 
isolated,  the  chances  are  many  to  one  against  the  same 
successful  experiments  in  combination  occurring  in  each  of 
the  two  groups.  Hence  it  follows  that  the  progress  or 

*  "  In  every  case  there  are  two  factors,  namely,  the  nature  of  the  organism 
and  the  nature  of  the  conditions.  The  former  seems  to  be  much  the  more 
important ;  for  nearly  similar  variations  sometimes  arise  under,  as  far  as  we 
can  judge  dissimilar  conditions ;  and,  on  the  other  hand,  dissimilar  variations 
arise  under  conditions  which  appear  to  be  nearly  uniform"  ("Origin  of 
Species,"  p.  6). 


Variation  and  Natural  Selection.  109 

advance  in  the  two  groups,  though  analogous,  would  not  be 
identical,  and  divergence  would  thus  be  possible  under 
practically  similar  conditions  of  life. 

In  his  observations  on  the  terrestrial  molluscs  of  the 
Sandwich  Islands,  Mr.  Gulick  notes  that  different  forms 
are  found  in  districts  which  present  essentially  the  same 
environment,  and  that  there  is  no  greater  divergence  when 
the  climatic  conditions  are  dissimilar  than  there  is  when 
those  conditions  are  similar.  As  before  noticed,  the  degree 
of  divergence  is,  roughly  speaking,  directly  as  the  distance 
the  varietal  forms  are  apart.  Again,  Darwin  notes  that 
the  climate  and  environment  in  the  several  islands  of  the 
Galapagos  group  are  much  the  same,  though  each  island 
has  a  somewhat  divergent  fauna  and  flora.  These  facts 
lend  countenance  to  the  view  that  divergence  can  and  does 
occur  under  similar  conditions  of  life,  if  there  be  isolation. 
They  seem,  also,  so  far  as  they  go,  to  negative  the  view  - 
that  the  species  is  moulded  directly  by  the  external  con- 
ditions. For,  if  this  factor  were  powerful,  it  would  over- 
ride the  effects  of  experimental  combination  of  characters 
when  the  conditions  were  similar,  and  would  give  rise 
to  well-marked  varietal  forms  when  the  conditions  were 
diverse. 

If  we  admit  preferential  breeding  as  a  segregation-factor 
(and  arising  out  of  it  sexual  selection,  in  a  modified  form, 
as  a  determining  one  in  the  evolution  of  the  plumage  of 
male  birds),  it  is  evident  that  the  standard  of  recognition- 
marks  can  only  be  maintained  by  a  uniformity  of  preference 
or  taste.  Still,  the  uniformity  is  not  likely  to  be  absolute. 
In  this  matter,  as  in  others,  variations  will  occur,  and 
after  the  lapse  of  a  thousand  generations,  in  which  elimina- 
tion has  been  steadily  at  work,  it  is  hardly  probable  that 
the  recognition  standard  would  remain  absolutely  un- 
changed. For,  though  there  may  not  be  any  direct 
elimination  in  this  particular  respect,  there  might  well  be 
colour-eliminations  in  other  (e.g.  protective)  respects,  and 
the  mental  nature  would  not  remain  quite  unchanged. 
Moreover,  we  know  that  secondary  sexual  characters  are 


no  Animal  Life  and  Intelligence. 

remarkably  subject  to  variation,  as  may  be  well  seen  in  the 
case  of  ruffs  (Machetes  pugnax)  in  the  British  Natural 
History  Museum.  In  the  case  of  our  two  islands  with 
isolated  faunas,  therefore,  if  they  formed  separate  breeding- 
areas  for  birds,  the  chances  would  be  many  to  one  against 
the  change  in  the  standard  of  recognition -marks  being 
identical  in  each  area.  Hence  might  arise  those  minute 
but  definite  specific  distinctions  which  are  so  noteworthy 
in  this  class  of  the  animal  kingdom.  Instance  the  Old  and 
New  World  species  of  teal,  the  Eastern  and  Western  species 
of  curlew  and  whimbrel,  and  other  cases  numerous.*  This, 
in  fact,  is  probably  in  many  cases  the  true  explanation  of 
the  occurrence  of  representative  species,  slight  specific 
variations  of  the  same  form  as  it  is  traced  across  a  conti- 
nent or  through  an  archipelago  of  islands. 

The  question  has  been  raised,  and  of  late  a  good  deal 
discussed,  whether  specific  characters,  those  traits  by 
which  species  are  distinguishable,  are  always  of  use  to  the 
species  which  possess  them.  Here  it  is  essential  to  define 
what  is  meant  by  utility.  Characters  may  be  of  use  in 
enabling  the  possessor  to  resist  elimination;  or,  like  the 
colours  of  flowers,  they  may  be  of  use  in  attracting  insects, 
and  thus  furthering  selection ;  or,  like  recognition-marks, 
they  may  be  of  use  in  effecting  segregation.  This  last  form 
of  utility  is  apt  to  be  overlooked  or  lost  sight  of.  In  speak- 
ing of  humming-birds,  the  Duke  of  Argyll  says  that  "  a  crest 
of  topaz  is  no  better  in  the  struggle  for  existence  than  a 
crest  of  sapphire.  A  frill  ending  in  spangles  of  the  emerald 
is  no  better  in  the  battle  of  life  than  a  frill  ending  in 
spangles  of  the  ruby."  But  if  these  characters  be  recog- 
nition-marks, they  may  be  of  use  in  segregation.  They  are 
a  factor  in  isolation.  But  it  may  be  further  asked — What 
is  the  use  of  the  segregation  ?  Wherein  lies  the  utility  of 
the  divergence  into  two  forms  ?  This  question,  however, 
involves  a  complete  change  of  view-point.  The  question 
before  us  is  whether  specific  characters  are  of  use  to  the 

*  See  "  Evolution  without  Natural  Selection,"  by  Charles  Dixon.     This 
author's  facts  are  valuable ;  his  theories  are  ill  digested. 


Variation  and  Natural  Selection.  1 1 1 

species  which  possesses  them.  To  this  question  it  is  sufficient 
to  answer  that  they  are  useful  in  effecting  or  preserving 
segregation,  without  which  the  species,  as  a  distinct  species, 
would  cease  to  exist.  We  are  not  at  present  concerned 
with  the  question  whether  divergence  in  itself  is  useful  or 
advantageous.  If  it  be  pressed,  we  must  reply  that,  although 
divergence  is  undoubtedly  of  immense  advantage  to  life  in 
general,  enabling,  as  Darwin  said,  its  varying  and  diver- 
gent forms  to  become  adapted  to  many  and  highly  diversified 
places  in  the  economy  of  nature,  still  in  many  individual 
cases  it  is  neither  possible  nor  in  any  respect  necessary  to 
our  conception  of  evolution  to  assign  any  grounds  of  utility 
or  advantage  for  the  divergence  itself. 

In  any  case,  we  are  dealing  at  present  with  the  utility 
of  specific  characters  to  the  species  which  possess  them  ; 
and  under  the  head  of  utility  we  are  including  usefulness 
in  effecting  or  maintaining  segregation.  Now,  we  have 
already  seen  that  variations  may  be  either  advantageous 
(useful),  or  neutral  (useless),  or  disadvantageous  (worse 
than  useless).  The  latter  class  we  may  here  disregard; 
elimination  will  more  or  less  speedily  dispose  of  them. 
With  regard  to  neutral  (useless)  variations,  we  must  also 
note  that  they  may  be  correlated  with  variations  of  the 
other  two  classes.  If  correlated  with  disadvantageous 
variations,  they  will  be  eliminated  along  with  them;  if 
correlated  with  advantageous  variations,  they  will  escape 
elimination  (or  will  be  selected)  together  with  them.  There 
remain  neutral,  or  useless,  variations,  not  correlated  with 
either  of  the  other  two  classes.  Are  these  in  any  cases 
distinctive  of  species  ? 

It  is  characteristic  of  specific  distinctions  that  they  are 
relatively  constant.  Elimination,  selection,  or  preferential 
breeding  gives  them  relative  fixity.  On  the  other  hand,  it 
is  characteristic  of  neutral  variations  that  they  are  incon- 
stant. There  is  nothing  to  give  them  fixity.  It  is,  of 
course,  conceivable  that  all  the  migrants  to  a  new  area 
were  possessed  of  a  useless  neutral  character,  which  those 
in  the  mother  area  did  not  possess  ;  or  that  such  a  useless 


1 1 2  Animal  Life  and  Intelligence. 

character  was  in  them  preponderant,  and  by  intercrossing 
formed  a  less  fluctuating,  useless  character  than  their  pro- 
genitors exhibited.  Still,  the  extensive  occurrence  of  such 
neutral,  or  useless,  characteristics  would  be  in  the  highest 
degree  improbable.  Our  ignorance  often  prevents  us  from 
saying  in  what  particular  way  a  character  is  useful.  We 
must  neither,  on  the  one  hand,  demand  proof  that  this, 
that,  or  the  other  specific  character  is  useful,  nor,  on  the 
other  hand,  demand  negative  evidence  (obviously  impos- 
sible to  produce)  that  it  is  without  utilitarian  significance ; 
but  we  may  fairly  request  those  who  believe  in  the  wide 
occurrence  of  useless  specific  characters  to  tell  us  by  what 
means  these  useless  characters  have  acquired  their  relative 
constancy  and  fixity.  A  suggestion  on  this  head  will  be 
found  in  the  next  chapter. 

We  must  now  pass  on  to  consider  briefly  a  most  im- 
portant factor  in  the  struggle  for  existence.  Hitherto  we 
have  regarded  this  struggle  as  uniform  in  intensity;  we 
must  now  regard  it  as  variable,  with  alternations  of  good 
times  and  hard  times,  and  indicate  the  causes  to  which 
such  variations  are  due. 

With  variations  of  climate,  such  as  we  know  to  occur 
from  year  to  year,  or  from  decade  to  decade,  there  are 
variations  in  the  productiveness  of  the  soil ;  and  when  we 
remember  how  closely  interwoven  are  the  web  and  woof  of 
life,  we  shall  see  that  the  increased  or  diminished  produc- 
tiveness of  any  area  will  affect  for  good  or  ill  all  the  life 
which  that  area  supports.  The  introduction  of  new  forms 
of  life  into  an  area,  or  their  preponderance  at  certain 
periods  owing  to  climatic  or  other  conditions  particularly 
favourable  to  them  as  opposed  to  other  forms,  may  alter 
the  whole  balance  of  life  in  the  district.  We  are  often 
unable  to  assign  any  reason  for  the  sudden  increase  or 
diminution  of  the  numbers  of  a  species ;  we  can  only  pre- 
sume that  it  is  the  result  of  some  favourable  or  unfavour- 
able change  of  conditions.  Thus  Mr.  Alexander  Becker  * 
has  recently  drawn  attention  to  the  fact  that  whereas  for 

*  Nature,  vol.  xlii.  p.  136. 


Variation  and  Natural  Selection.  113 

several  years  various  species  of  grasshoppers  appeared  in 
great  numbers  in  South-east  Bussia,  there  came  then  one 
year  of  sudden  death  for  most  of  them.  They  were  sitting 
motionless  on  the  grasses  and  dying.  He  gives  similar 
cases  of  butterflies  for  a  while  numerous,  and  then  rare, 
and  states  that  a  squirrel  common  near  Sarepta  suddenly 
disappeared  in  the  course  of  one  summer,  probably,  he 
adds,  succumbing  to  some  contagious  disease.  Such  is  the 
nice  balance  of  life,  that  the  partial  disappearance  of  a 
single  form  may  produce  remarkable  and  little-expected 
effects.  Darwin  amusingly  showed  how  the  clover  crops 
might  be  beneficially  affected  by  the  introduction  of  a 
family  of  old  maids  into  a  parish.  The  clover  is  fertilized 
by  humble-bees,  the  bees  are  preyed  upon  by  mice ;  the 
relations  between  cats  and  mice,  and  between  old  maids 
and  cats,  are  well  known  and  familiar :  more  old  maids, 
more  cats  ;  more  cats,  less  mice  ;  less  mice,  more  humble- 
bees  ;  more  humble-bees,  better  fertilization.  A  little  thing 
may  modify  the  balance  of  life,  and  increase  or  diminish 
the  struggle  for  existence,  and  the  rigour  of  the  process  of 
elimination. 

But  when  we  take  a  more  extended  view  of  the  matter, 
and  include  secular  changes  of  climate,  the  possible  range 
of  variation  in  the  struggle  for  existence  is  seen  to  be 
enormously  increased.  It  is  well  known  to  those  who  have 
followed  the  progress  of  geology,  that  in  early  Kainozoic 
times  a  mild  climate  extended  to  within  the  Arctic  circle, 
while  during  the  glacial  epoch  much  of  the  north  tempe- 
rate zone  was  fast  locked  in  ice,  and  the  climate  of  the 
northern  hemisphere  was  profoundly  modified.  The  animals 
in  the  north  temperate  zone  were  driven  southwards.* 
Not  only  was  there  much  elimination  from  the  severe 
climatic  conditions,  but  the  migrants  were  driven  south- 
wards into  areas  already  well  stocked  with  life,  and  the 

*  We  may  here  note,  in  passing,  the  fact  that  the  changes  of  life-forms  in  a 
succession  of  beds  points  jn  nine  cases  out  of  ten  rather  to  substitution  through 
migration  than  to  transmutation.  Still,  there  are  notable  cases  of  trans- 
mutation, as  in  the  fresh-water  Planorbes  of  Steinhem,  in  Wittenberg  (described, 
after  Hilgendorf,  by  0.  Schmidt,  "  The  Doctrine  of  Descent,"  p.  96). 

I 


1 14  Animal  Life  and  Intelligence. 

competition  for  means  of  subsistence  in  these  areas  must 
have  been  rendered  extremely  severe.  Elimination  was  at 
a  maximum.  Then  followed  the  withdrawal  of  glacial 
conditions.  The  increasing  geniality  of  the  climate  allowed 
an  expansion  of  life  within  a  given  area,  and  the  with- 
drawal of  snow  and  ice  further  and  further  north  set  free 
new  areas  into  which  this  expanding  life  could  migrate 
and  find  subsistence.  The  hard  times  of  the  glacial  period 
were  succeeded  by  good  times  of  returning  warmth  and  an 
expanding  area ;  and  if,  as  some  geologists  believe,  there 
was  an  inter-glacial  period  (or  more  than  one  such  period) 
in  the  midst  of  the  Great  Ice  Age,  then  hard  times  and 
good  times  alternated  during  the  glacial  epoch. 

Expansion  and  contraction  of  life-areas  have  also  been 
effected  again  and  again  in  the  course  of  geological  history 
by  elevations  and  subsidences  of  the  land.  At  the  beginning 
of  Mesozoic  times  much  of  Europe  was  dry  land.  In 
Triassic  and  Khaetic  times  there  were  lakes  in  England  and 
in  Germany,  and  a  warm  Mediterranean  Sea  to  the  south. 
Subsidence  of  the  European  area  brought  with  it  a  lessened 
land-area  and  an  increased  sea-area :  bad  times  and  in- 
creased competition  for  land  animals  ;  good  times  and 
a  widening  life-area  for  marine  forms  of  life.  This  con- 
tinued, with  minor  variations,  till  its  culmination  in  the 
Cretaceous  period.  Then  came  the  converse  process :  the 
land-areas  increased,  the  sea  was  driven  back.  A  good 
time  had  come  for  terrestrial  life ;  the  marine  inhabitants 
of  estuaries  and  inland  seas  felt  the  pressure  of  increased 
competition  in  a  lessening  area.  And  so  there  emerged 
the  continental  Europe  of  the  beginning  of  the  Kainozoic 
era.  And  it  is  scarcely  necessary  to  remind  those  who 
are  in  any  degree  conversant  with  geology  that  during 
tertiary  times  there  have  been  alternate  expansions  and 
contractions  of  life-areas,  marine  and  terrestrial,  the  former 
bringing  good  times,  the  latter  hard  times  and  a  heightened 
struggle  for  existence. 

Now,  what  would  be  the  result  of  this  alternation  of 
good  times  and  hard  times  ?  During  good  times  varieties, 


Variation  and  Natiiral  Selection.  115 

which  would  be  otherwise  unable  to  hold  their  own,  might 
arise  and  have  time  to  establish  themselves.  In  an  ex- 
panding area  migration  would  take  place,  local  segregation 
in  the  colonial  areas  would  be  rendered  possible,  differential 
elimination  in  the  different  migration-areas  would  produce 
divergence.  There  would  be  diminished  elimination  of 
neutral  variations,  thus  affording  opportunities  for  experi- 
mental combinations.  In  general,  good  times  would  favour 
variation  and  divergence. 

Intermediate  between  good  times  and  hard  times  would 
come,  in  logical  order,  the  times  in  which  there  is  neither 
an  expansion  nor  a  contraction  of  the  life-area.  One  -may 
suppose  that  these  are  times  of  relatively  little  change. 
There  is  neither  the  divergence  rendered  possible  by  the 
expansion  of  life-area,  nor  the  heightened  elimination 
enforced  by  the  contraction  of  life-area.*  Elimination  is 
steadily  in  progress,  for  the  law  of  increase  must  still 
hold  good.  Divergence  is  still  taking  place,  for  the  law  of 
variation  still  obtains.  But  neither  is  at  its  maximum. 
These  are  the  good  old-fashioned  times  of  slow  and  steady 
conservative  progress.  They  are,  perhaps,  well  exemplified 
by  the  fauna  of  the  Carboniferous  period,  and  it  is  not  at 
all  improbable  that  we  are  ourselves  living  in  such  a  quiet, 
conservative  period. 

On  the  other  hand,  hard  times  would  mean  increased 
elimination.  During  the  exhibitions  at  South  Kensington 
there  were  good  times  for  rats.  But  when  the  show  was 
over,  there  followed  times  that  were  cruelly  hard.  The 
keenest  competition  for  the  scanty  food  arose,  and  the  poor 
animals  were  forced  to  prey  upon  each  other.  "  Their 
cravings  for  food,"  we  read  in  Nature,  "  culminated  in  a 
fierce  onslaught  on  one  another,  which  was  evidenced  by 
the  piteous  cries  of  those  being  devoured.  The  method  of 
seizing  their  victims  was  to  suddenly  make  a  raid  upon 

*  I  would  ask  historians  whether  there  have  not  been,  in  English  history, 
good  times  of  free  and  beneficial  divergence  exemplified  in  diverse  intellectual 
activity,  hard  times  of  rigorous  elimination,  and  intermediate  times  of  placid, 
somewhat  humdrum  conservatism. 


n6  Animal  Life  and  Intelligence. 

one  weaker  or  smaller  than  themselves,  and,  after  over- 
powering it  by  numbers,  to  tear  it  in  pieces."  Elimination 
by  competition,  passing  in  this  way  into  elimination  by 
battle,  would,  during  hard  times,  be  increased.  None  but 
the  best  organized  and  best  adapted  could  hope  to  escape. 
There  would  be  no  room  for  neutral  variations,  which,  in 
the  keenness  of  the  struggle,  would  be  relatively  disadvan- 
tageous. Slightly  divergent  varieties,  before  kept  apart 
through  local  segregation,  would  be  brought  into  com- 
petition. The  weakest  would  in  some  cases  be  eliminated. 
In  other  cases,  the  best-adapted  individuals  of  each  variety 
might  survive.  If  their  experiments  in  intercrossing, 
should  such  occur,  gave  rise  to  fertile  offspring,  more 
vigorous  and  better  adapted  than  either  parent-race,  these 
would  survive,  and  the  parent-forms  would  be  eliminated. 
But  if  such  experiments  in  intercrossing  gave  rise  to 
infertile,  weakly  offspring,  these  would  be  eliminated.  Thus 
sterility  between  species  would  become  fixed.  Wherever, 
during  the  preceding  good  times,  divergence  had  taken 
place  in  two  different  directions  of  adaptation,  and  some 
intermediate  forms,  fairly  good  in  both  directions,  had  been 
able  to  escape  elimination,  the  chances  are  that  these  inter- 
mediates would  be  hi  hard  times  eliminated,  and  the 
divergent  forms  left  in  possession  of  the  field.  Wherever, 
during  good  times,  a  species  had  acquired  or  retained  a 
habit  of  flexibility,  that  habit  would  stand  it  in  good  stead 
in  the  midst  of  the  changes  wrought  by  hard  times ;  but 
when  it  had,  on  the  other  hand,  acquired  rigidity  (like  the 
proverbially  "  inflexible  goose  "),  it  would  be  at  a  disadvan- 
tage in  the  stress  of  a  heightened  elimination. 

The  alternation  of  good  times  and  hard  times  may  be 
illustrated  by  an  example  taken  from  human  life.  The 
introduction  of  ostrich-farming  in  South  Africa  brought 
good  times  to  farmers.  Whereupon  there  followed  diver- 
gence in  two  directions.  Some  devoted  increased  profits  to 
improvements  upon  their  farms,  to  irrigation  works  which 
could  not  before  be  afforded,  and  so  forth.  For  others  in- 
creased income  meant  increased  expenditure  and  an  easier, 


Variation  and  Natural  Selection.  117 

if  not  more  luxurious,  mode  of  life.  Then  came  hard  times. 
Others,  in  Africa  and  elsewhere,  learnt  the  secret  of  ostrich- 
farming.  Competition  brought  down  profits,  and  elimina- 
tion set  in — of  which  variety  need  hardly  be  stated. 

I  believe  that  the  alternation  of  good  times  and  hard 
times,  during  secular  changes  of  climate  and  alternate  ex- 
pansions and  contractions  of  life-areas  through  geological 
upheavals  and  depression  of  the  land,  has  been  a  factor  of 
the  very  greatest  importance  in  the  evolution  of  varied  and 
divergent  forms  of  life,  and  in  the  elimination  of  inter- 
mediate forms  between  adaptive  variations.  It  now  only 
remains  in  this  chapter  to  say  a  few  words  concerning  con- 
vergence, adaptation,  and  progress. 

Convergence,  which  is  the  converse  of  divergence,  is 
brought  about  through  the  adaptation  of  different  forms 
of  life  to  similar  conditions  of  existence.  The  somewhat 
similar  form  of  the  body  and  fin-like  limbs  of  fishes,  of 
ancient  reptiles  (the  ichthyosaurus  and  its  allies),  of  whales, 
seals,  and  manatees,  is  a  case  in  point.  Both  birds,  bats, 
and  pterodactyls  have  keeled  breastbones  for  the  attach- 
ment of  the  large  muscles  for  flight.  A  whole  series  of 
analogous  adaptations,  as  the  result  of  analogous  modes  of 
life,  are  found  in  the  placental  mammals  of  Europe  and 
Asia,  on  the  one  hand,  and  the  marsupial  forms  of  Australia 
on  the  other  hand.  The  flying  squirrel  answers  to  the 
flying  phalanger,  the  fox  to  the  vulpine  phalanger,  the  bear 
to  the  koala,  the  badger  to  the  pouched  badger,  the  rabbit 
to  the  bandicoot,  the  wolverine  to  the  Tasmanian  devil,  the 
weasel  to  the  pouched  weasel,  the  rats  and  mice  to  the 
kangaroo  rats  and  mice,  and  so  on.  A  familiar  example 
of  convergence  is  to  be  seen  in  our  swallows  and  martins, 
on  the  one  hand,  and  the  swifts  on  the  other.  Notwith- 
standing their  superficial  similarity  in  external  form  and 
habits,  they  are  now  generally  regarded  as  belonging  to 
distinct  orders  of  birds. 

These    are   examples    of    convergence.*      Animals   of 

*  Two  more  teshnical  examples  may  be  noticed  in  a  note.    (1)  Professor 
Haeckel  has   recently  (Challenger    Keports,   vol.   xxviii.)   shown   that  the 


n8  Animal  Life  and  Intelligence. 

diverse  descent  and  ancestry  have,  through  similarity  of 
surrounding  conditions  or  of  habits  of  life,  become,  in 
certain  respects,  assimilated.  But  some  zoologists  go 
further  than  this.  They  maintain  that  the  same  genus 
or  species  may,  through  adaptation  to  similar  circum- 
-stances,  be  derived  from  dissimilar  ancestors.  Some 
palaeontologists,  for  example,  believe  that  the  horse  has 
been  independently  evolved  along  parallel  lines  in  Europe 
and  in  America.  Professor  Cope  considers  that  in  the  one 
continent  Protohippus,  and  in  the  other  Hipparion,  was  the 
immediate  ancestor  of  Equus.  The  probabilities  are,  how- 
ever, so  strongly  against  such  a  view,  that  it  cannot  be 
accepted  until  substantiated  by  stronger  evidence  than  is 
yet  forthcoming. 

A  special  and  particular  form  of  convergence,  at  any 
rate  in  certain  obvious,  if  superficial,  characters,  has  already 
been  noticed  in  our  brief  consideration  of  mimicry.  In 
the  first  place,  among  a  number  of  closely  related  species 
of  inedible  butterflies,  the  tendency  to  divergence  is  checked, 
so  far  as  external  markings  and  coloration  are  concerned, 
that  all  may  continue  to  profit  by  the  resemblance,  and 
that  the  numbers  tasted  by  young  birds  in  gaining  their 
experience  (for  the  avoidance  seems  to  be  at  most  incom- 
pletely instinctive)  may  be  divided  amongst  all  the  species, 
thus  lessening  the  loss  to  each.  Secondly,  there  may  be  a 
convergence  of  certain  genera  of  distantly  related  inedible 
groups  (e.g.  among  the  Heliconidae  and  the  Danaidae),  which 
gain  by  being  apparently  one  species,  since  the  loss  from 
young  birds  is  shared  between  them.  And  lastly,  there  is 
the  true  mimicry  of  quite  distinct  families  of  butterflies, 
not  themselves  inedible,  but  sheltering  themselves  under 

Siphonophora  include  two  groups,  closely  resembling  each  other,  but  of 
different  ancestry:  (a)  The  Disconanthro,  traceable  to  trachomedusoid 
ancestors ;  (6)  the  Siphonanthae,  traceable  to  anthomedusoid  ancestors  like 
Sarsia.  (2)  M.  Paul  Pelseneer  has  beeH  led  to  the  conclusion  that  the 
pteropod  molluscs  also  include  two  groups  resembling  each  other,  but  of 
different  ancestry  :  (a)  The  Thecosomes,  traceable  to  tornatellid  ancestors ; 
(fc)  the  Gymnosomes,  traceable  to  aphysiid  ancestors.  In  each  case,  the 
ancestral  sea-slug  has  been  modified  for  a  free-swimming  life. 


Variation  and  Natural  Selection.  1 1 9 

the  guise  and  sharing  the  bad  reputation  of  the  mimicked 
forms.  Such  forms  of  convergence  are  in  special  adaptation 
to  a  very  special  environment. 

We  must  remember  that  in  all  cases  adaptation  is  a 
matter  of  life  and  environment.  And  these,  we  may  now 
note,  may  be  related  in  one  or  more  of  three  ways.  In 
the  first  place,  there  is  the  adaptation  of  life  to  an  un- 
changing environment ;  for  example,  the  adaptation  of  all 
forms  of  life  to  the  fixed  and  unchanging  properties  of 
inorganic  matter.  If  we  liken  life  to  a  statue  and  the 
environment  to  a  mould  in  which  it  is  cast,  we  have  in 
this  case  a  rigid  mould  and  a  plastic  statue.  Secondly, 
the  adaptation  may  be  mutual,  as,  for  example,  when  the 
structures  of  insects  and  flowers  are  fitted  each  to  the 
other,  or  when  the  speed  of  hunters  and  hunted  is  steadily 
increased  through  the  elimination  of  the  slow  in  either 
group.  Here  the  mould  and  statue  are  both  somewhat 
plastic,  and  yield  to  each  other's  influence.  Thirdly,  the 
environment  may  be  moulded  to  life.  This,  again,  is  only 
relative,  since  life  never  wholly  loses  its  plasticity.  The 
bird  that  builds  a  nest,  the  beaver  that  constructs  a  dam, 
the  insect  that  gives  rise  to  a  gall, — these,  so  far,  mould 
the  environment  to  the  needs  of  their  existence.  Man  in 
especial  has  the  power,  through  his  developed  intelligence, 
of  manufacturing  his  own  environment.  Here  the  statue 
is  relatively  rigid,  and  the  mould  plastic. 

Progress  may  be  defined  as  continuous  adaptation.  In 
modern  phrase,  this  is  called  evolution.  The  continuity 
makes  the  difference  between  evolution  and  revolution. 
Both  are  natural.  Both  occur  in  the  organic,  the  social, 
and  the  intellectual  sphere.  Evolution  is  the  orderly 
progress  of  the  organism  or  group  of  organisms,  by  which 
it  becomes  more  and  more  in  harmony  with  surrounding 
conditions.  If  the  conditions  become  more  and  more  com- 
plex, the  organism  will  progress  in  complexity ;  but  if  the 
conditions  be  more  and  more  simple,  progress  (if  such  it 
may  still  be  called)  will  be  towards  simplicity  of  structure, 
unnecessary  complexity  being  eliminated,  or,  in  any  case, 


I2O  Animal  Life  and  Intelligence. 

disappearing.  Hence,  in  parasites  and  some  forms  of  life 
which  live  under  simple  conditions,  we  have  the  phenomena 
of  degeneration,  or  a  passage  from  a  more  complex  to  a 
more  simple  condition. 

Revolution  in  organic  life  is  the  destruction  of  one 
organism  or  group  of  organisms,  and  the  replacement  in 
its  stead  of  a  wholly  different  organism  or  group  of 
organisms.  During  hard  times  there  may  be  much  revo- 
lution, or  replacement  of  one  set  of  organic  forms  by 
another  set  of  organic  forms.  It  was  by  revolution  that 
the  dominant  reptiles  of  the  Mesozoic  epoch  were  replaced 
by  the  dominant  mammals  of  Kainozoic  times.  It  was  by 
revolution  that  pterodactyls  were  supplanted  by  birds. 
Revolution  has  exterminated  many  a  group  in  geological 
ages.  On  the  other  hand,  it  was  by  evolution  that  the 
little-specialized  Eocene  ungulates  gave  rise  to  the  horse, 
the  camel,  and  the  deer ;  by  divergent  evolution  that  the 
bears  and  dogs  were  derived  from  common  ancestors. 
Palaeontology  testifies  both  to  evolution  and  revolution.* 
That  history  does  the  same,  I  need  not  stay  to  exemplify. 
The  same  laws  also  apply  to  systems  of  thought.  Dar- 
winism has  revolutionized  our  conceptions  of  nature. 
Darwin  placed  upon  a  satisfactory  basis  a  new  order  of 
interpretation  of  the  organic  world.  By  it  other  interpre- 
tations have  been  supplanted.  And  now  this  new  concep- 
tion is  undergoing  evolution,  not  without  some  divergence. 

In  this  chapter  we  have  seen  how  evolution  is  possible 
under  natural  conditions.  If  the  law  of  increase  be  true, 
if  more  are  born  than  can  survive  to  procreate  their  kind, 
natural  selection  is  a  logical  necessity.  We  must  not 
blame  our  forefathers  for  not  seeing  this.  Until  geology 
had  extended  our  conception  of  time,  no  such  conclusions 
could  be  drawn.  If  organisms  have  existed  but  six  or 
seven  thousand  years,  and  if  in  the  last  thousand  years 
little  or  no  change  in  organic  life  has  occurred,  the 
supposition  that  they  could  have  originated  by  any  such 

*  For    evidence    in    copious    abundance,  see    Nicholson's    "Manual  of 
Palaeontology,"  new  edition,  vol.  i. :  "  Vertebrata,"  by  K.  Lydekker. 


Variation  and  Natural  Selection.  121 

process  as  natural  selection  is  manifestly  absurd.  Lyell 
was  the  necessary  precursor  of  Darwin.  Given,  then, 
increase  and  elimination  throughout  geological  time, 
natural  selection  is  a  logical  necessity.  No  one  who 
adequately  grasps  the  facts  can  now  deny  it.  It  is  an 
unquestionable  factor  in  organic  evolution.  Whether  it  is 
the  sole  factor,  is  quite  another  matter,  and  one  we  will  / 
consider  in  the  chapter  on  "  Organic  Evolution." 


122  Animal  Life  and  Intelligence. 


CHAPTER  V. 

HEREDITY   AND    THE    ORIGIN   OF    VARIATIONS. 

THE  law  of  heredity,  I  have  said  above,  may  be  regarded 
as  that  of  persistence  exemplified  in  a  series  of  organic 
generations.  Variation  results — it  is  clear  that  it  must 
result — from  some  kind  of  differentiating  influence.  Such 
statements  as  these,  however,  though  they  are  true  enough, 
do  not  help  us  much  in  understanding  either  heredity  or 
variation. 

Let  us  first  notice  that  normal  cases  of  reproduction 
exemplify  both  phenomena — heredity  with  variation; 
hereditary  similarity  to  the  parents  in  all  essential  respects, 
individual  variations  in  minor  points.  This  is  seen  in 
man.  Brothers  and  sisters  may  present  family  resem- 
blances among  each  other  and  to  their  parents,  but  each 
has  individual  traits  of  feature  and  of  character.  Only  in 
particular  cases  of  so-called  "identical  twins"  are  the 
variations  so  slight  as  not  to  be  readily  perceptible  by  even 
a  casual  observer. 

Now,  when  we  seek  an  explanation  of  these  well-known 
facts,  we  may  be  tempted  to  find  it  in  the  supposition  that 
the  character  of  the  parents  does  not  remain  constant,  that 
the  character  influences  the  offspring,  and  that  therefore 
the  children  born  at  successive  periods  will  differ  from  each 
other,  while  twins  born  in  the  same  hour  will  naturally 
resemble  each  other.  As  Darwin  himself  says,*  "  The 
greater  dissimilarity  of  the  successive  children  of  the  same 
family  in  comparison  with  twins,  which  often  resemble 
each  other  in  external  appearance,  mental  disposition,  and 

*  "  Animals  and  Plants  under  Domestication,"  vol  ii.  p.  239. 


Heredity  and  the  Origin  of  Variations.      1 2  3 

constitution,  in  so  extraordinary  a  manner,  apparently 
proves  that  the  state  of  the  parents  at  the  exact  period  of 
conception,  or  the  nature  of  the  subsequent  embryonic 
development,  has  a  direct  and  powerful  influence  on  the 
character  of  the  offspring."  But  a  little  consideration  will 
show  that,  though  this  might,  in  the  absence  of  a  better 
explanation,  account  for  variation  in  character,  it  could  not 
account  for  variation  in  form  and  feature,  unless  we  regard 
these  as  in  some  way  determined  by  the  character.  More- 
over, as  we  shall  see  presently,  it  is  open  to  question 
whether  acquired  modifications  of  structure  or  character  in 
the  parent  can  in  any  way  influence  the  offspring.  Again, 
in  the  litter  of  puppies  born  of  the  same  bitch  by  the  same 
dog  there  are  individual  variations,  often  as  well  marked 
as  those  in  successive  births. 

The  facts,  then,  to  be  accounted  for  are — first,  the  close 
hereditary  resemblance  in  all  essential  points  of  offspring 
to  parent;  and,  secondly,  the  individual  differences  in 
minor  points  among  the  offspring  produced  simultaneously 
or  successively  by  the  same  parents.  These  are  the  facts 
as  they  occur  in  the  higher  animals.  It  will  be  well  to 
lead  up  to  our  consideration  of  them  by  a  preliminary 
survey  of  the  facts  as  they  are  exemplified  by  some  of  the 
lower  organisms. 

In  the  simpler  protozoa,  where  fission  occurs,  and  where 
the  organism  is  composed  of  a  single  cell,  where  also  there 
is  a  single  nucleus  which  apparently  undergoes  division 
into  two  equal  and  similar  parts,  it  is  easy  to  understand 
that  the  two  organisms  thus  resulting  from  the  halving  of 
a  single  organism  partake  completely  of  its  nature.  If  the 
fission  of  an  amoeba  is  such  as  to  divide  it  into  two  similar 
parts,  there  is  no  reason  why  these  two  similar  parts 
should  not  be  in  all  respects  alike,  and  should  not,  by  the 
assimilation  of  new  material,  acquire  the  size  and  all  the 
characteristics  of  the  parent  form.  In  the  higher  and 
more  differentiated  protozoa,  the  case  is  not  quite  so  simple; 
for  the  two  halves  are  not  each  like  the  whole  parent,  but 
have  to  be  remodelled  into  a  similar  organism.  But  if  we 


124  Animal  Life  and  Intelligence. 

suppose,  as  we  seem  to  hare  every  right  to  suppose,  that 
it  is  the  nucleus  that  controls  the  formative  processes  in 
the  cell,  there  is  not  much  difficulty  in  understanding  how, 
when  the  nucleus  divides  into  two  similar  portions,  each 
directs,  so  to  speak,  the  similar  refashioning  of  its  own 
separated  protoplasmic  territory. 

From  the  protozoa  we  may  pass  to  such  a  comparatively 
simple  metazoon  as  the  hydra.  Here  the  organism  is  com- 
posed, not  of  a  single  cell,  but  of  a  number  of  ce'lls.  These 
cells  are,  moreover,  not  all  alike,  but  have  undergone 
differentiation  with  physiological  division  of  labour.  There 
is  an  inner  layer  of  large  nutritive  cells,  and  an  outer  layer 
of  protective  cells,  some  of  which  are  conical  with  fine  pro- 
cesses proceeding  from  the  point  of  the  cone ;  others  are 
smaller,  and  fill  in  the  interstices  between  the  apices  of  the 
cones,  while  others  have  developed  into  thread-cells,  each 
with  a  fine  stinging  filament.  Between  the  two  layers 
there  is  a  thin  supporting  lamella.  The  essential  point  we 
have  here  to  notice  is  that  there  are  two  distinct  layers 
with  cells  of  different  form  and  function. 

Now,  it  has  again  and  again  been  experimentally  proved 
that  if  a  hydra  be  divided  into  a  number  of  fragments,  each 
will  grow  up  into  a  complete  and  perfect  hydra.  All  that 
is  essential  is  that,  in  the  separated  fragment,  there  shall 
be  samples  of  the  cells  of  both  layers.  Under  these  con- 
ditions, the  separated  cells  of  the  outer  layer  regenerate  a 
complete  external  wall,  and  the  separated  cells  of  the  inner 
layer  similarly  regenerate  a  complete  internal  lining.  From 
these  facts,  it  would  appear  that  such  a  small  adequately 
sampled  fragment  has  the  power,  when  isolated,  of 
assimilating  nutriment  and  growing  by  the  multiplication 
of  the  constituent  cells,  and  that  the  growth  takes  such 
lines  that  the  original  form  of  the  hydra  is  reproduced. 

Here  we  may  note,  by  way  of  analogy,  what  takes  place 
in  the  case  of  inorganic  crystals.  If  a  fragment  of  an 
alum  crystal  be  suspended  in  a  strong  solution  of  alum, 
the  crystal  will  be  recompleted  by  the  growth  of  new  parts 
along  the  broken  edges.  We  say  that  this  is  effected  under 


Heredity  and  the  Origin  of  Variations.     125 

the  influence  of  molecular  polarity.  Similarly,  we  may 
say  that  the  fragment  of  the  hydra  rebuilds  the  complete 
form  under  the  influence  of  an  hereditary  morphological 
tendency  residing  in  the  nuclei  of  the  several  cells.  The 
case,  though  still  comparatively  simple,  is  more  complex 
than  that  of  the  higher  protozoa.  There  the  divided  nucleus 
in  two  separated  cells  directs  each  of  these  in  hereditary 
lines  of  morphological  growth.  Here  not  only  do  the  cells 
and  their  nuclei  divide,  but  they  are  animated  by  a  common 
morphological  principle,  and  in  their  multiplication  combine 
to  form  an  organism  possessing  the  ancestral  symmetry. 
If,  however,  we  call  this  an  hereditary  morphological 
tendency  or  a  principle  of  symmetry;  or,  with  the  older 
physiologists,  a  nisus  formativus ;  or,  with  Darwin,  "  the 
co-ordinating  power  of  the  organization "  (all  of  these 
expressions  being  somewhat  unsatisfactory) ; — we  must 
remember  that  these  terms  merely  imply  a  play  of  molecular 
forces  analogous  to  that  which  causes  the  broken  crystal 
of  alum  to  become  recompleted  in  suitable  solution.  The 
inherent  molecular  processes  in  the  nuclei  *  in  the  one 
case  enable  the  cells  to  regenerate  the  hydra ;  the  inherent 
molecular  stresses  in  the  crystalline  fragment  in  the  other 
case  lead  to  the  reproduction  of  the  complete  crystal. 
In  either  case  there  is  no  true  explanation,  but  merely  a 
restatement  of  the  facts  under  a  convenient  name  or  phrase. 
The  power  of  regeneration  of  lost  parts,  which  is  thus 
seen  in  the  hydra,  is  also  seen,  in  a  less  degree  so  far  as 
amount  is  concerned,  but  in  a  higher  degree  so  far  as  com- 
plexity goes,  in  animals  far  above  the  hydra  in  the  scale  of 
life.  The  lobster  that  has  lost  a  claw,  the  snail  whose 
tentacle  has  been  removed,  the  newt  which  has  been  docked 
of  a  portion  of  its  tail  or  a  limb,  are  able  more  or  less  com- 
pletely to  regenerate  these  lost  parts.  And  the  regeneration 
may  involve  complex  structures.  With  the  tentacle  of  the 
snail  the  eye  may  be  removed,  and  this,  not  once  only,  but 

*  Or  in  certain  "  physiological  units  "  (Herbert  Spencer),  or  "  plastidules  " 
(Haeckel),  which  may  be  regarded  as  organic  molecules  exhibiting  their 
special  properties  under  vital  conditions. 


126  Animal  Life  and  Intelligence. 

a  dozen  times.  After  such  mutilation,  no  part  of  the  eye 
remains,  though  the  stump  of  its  nerve  is,  of  course,  left  ; 
still  the  perfect  organ  is  reconstructed  again  and  again,  as 
often  as  the  tentacle  is  removed.  The  cells  at  the  cut  end 
of  the  nerve-stump  divide  and  multiply,  as  do  also  those  of 
the  surrounding  tissues,  and  the  growing  nerve  terminates 
in  an  optic  cup,  as  it  did  previously  under  the  influences  of 
normal  development  before  the  mutilation.  Here  we  have 
phenomena  analogous  to,  and  in  some  respects  more  com- 
plex than,  those  which  are  seen  in  the  regenerative  process 
in  hydra.  It  is  well  known,  however,  that,  in  the  case  of 
higher  animals,  in  birds  and  mammals,  this  power  of 
regenerating  lost  parts  does  not  exist.  When  a  bone  is 
broken,  osseous  union  of  the  broken  pieces  may  indeed  take 
place ;  and  in  flesh-wounds,  the  gash  is  filled  in  and  heals 
over,  not  without  permanent  signs  of  its  existence,  as  may 
often  be  seen  in  the  faces  of  German  students.  But  beyond 
this  there  is  normally  no  regeneration.  The  soldier  who 
has  lost  an  arm  in  battle  cannot  return  home  and  in  quiet 
seclusion  reproduce  a  new  limb.  That  which  seems  to  be 
among  lower  animals  a  well-established  law  of  organic 
growth  does  not  here  obtain.  This  is  probably  due  to  the 
fact  that  the  higher  histological  differentiation  of  the  tissues 
in  the  more  highly  developed  forms  of  life  is  a  bar  to 
regeneration.  In  their  devotion  to  special  and  minute 
details  of  physiological  work,  the  cells  have,  so  to  speak, 
forgotten  their  more  generalized  reproductive  faculties. 
In  any  case,  however  the  fact  is  to  be  explained,  the 
higher  organisms  have  in  many  cases  almost  completely 
lost  the  power  of  regenerating  lost  parts.  But  this  loss  of 
the  regenerative  power  in  the  more  highly  differentiated 
animals  does  not  alter  or  invalidate  the  law  of  organic 
growth  we  are  considering.  The  law  may  be  thus  stated : 
Whenever,  after  mutilation,  free  growth  of  the  mutilated  surface 
occurs,  that  growth  is  directed  in  such  lines  as  to  reproduce 
the  lost  part  and  restore  the  symmetrical  integrity  of  the 
organism.  This  is  a  matter  of  heredity.  And  we  may 
regard  the  hereditary  reconstructive  power  as  residing 


Heredity  and  the  Origin  of  Variations.      127 

either  (1)  in  those  cells  at  or  adjoining  the  mutilated 
surface  which  are  concerned  in  the  regrowth  of  the  lost 
part ;  or  (2)  in  the  general  mass  of  cells  of  the  mutilated 
organism. 

There  are  difficulties  in  either  view.  Professor  Sollas, 
supporting  the  former,  says,*  "  This  power  [in  the  snail] 
of  growing  afresh  so  complex  and  specialized  an  organ  as 
an  eye  is  certainly,  at  first  sight,  not  a  little  astonishing, 
but  it  appears  to  be  capable  of  a  very  simple  explanation. 
The  cells  terminating  the  cut  stump  of  the  tentacle  are  the 
ancestors  of  those  which  are  removed;  a  fresh  series  of 
descendants  are  derived  from  them,  similarly  related  to  the 
ancestral  cells  as  their  predecessors  which  they  replace  ; 
the  first  generation  of  descendants  become  in  turn  ancestors 
to  a  second  generation,  similarly  related  to  them  as  were 
the  second  tier  of  extirpated  cells ;  and  this  process  of 
descent  being  repeated,  the  completed  organ  will  at  length 
be  rebuilt."  This  explanation  is,  however,  misleading  in 
its  simplicity.  The  cells  terminating  the  cut  stump  are 
not  the  direct  ancestors  of  those  which  are  removed,  except 
in  the  same  sense  as  gorillas  are  ancestors  of  men.  They 
are  rather  collateral  descendants  of  common  ancestors.  I 
think  that  Professor  Sollas  would  probably  agree  that, 
though  the  lens  and  "  retina "  are  of  epiblastic  (outer 
layer)  origin,  their  relationship  with  the  epiblastic  cells  at 
the  cut  stump  is  a  somewhat  distant  one.  In  the  repro- 
duction of  the  lens  the  cell-heredity  is  not  direct,  but 
markedly  indirect.  And  it  is  somewhat  difficult  to  under- 
stand by  what  means  the  ordinary  epiblastic  cells  of  the 
cut  stump,  which  have  had  no  part  in  the  special  and 
peculiar  work  of  lens-production,  should  be  enabled  to 
produce  cell-offspring,  some  of  which,  and  those  in  a 
special  relation  to  other  deeper-lying  cells,  possess  this 
peculiar  power. 

On  the  other  hand,  if  we  turn  to  the  view  that  the 
reproduction  is  effected,  not  by  the  cells  of  the  cut  surface 
alone,  but  by  the  general  mass  of  cells  in  the  mutilated 

*  Nature,  vol.  xxxix.  p.  486. 


128  Animal  Life  and  Intelligence. 

organism,  we  have  to  face  the  difficulty  of  understanding 
how  the  influence  of  cells  other  than  those  partaking  in 
the  regrowth  can  be  brought  to  bear  on  these  so  as  to 
direct  their  lines  of  development.  If  we  say  that  the 
organism  is  pervaded  by  a  principle  of  symmetry  such 
that  both  growth  and  regrowth,  whenever  they  take  place, 
are  constrained  to  follow  the  lines  of  ancestral  symmetry, 
we  are  really  doing  little  more  than  restating  the  facts 
without  affording  any  real  organic  explanation.  That 
which  we  want  to  know  is  in  what  organic  way  this  sym- 
metrical growth  is  effected — how  the  hereditary  tendency  is 
transmitted  through  the  nuclear  network  which  is  concerned 
in  cell-division.  I  do  not  think  that  we  are  at  present  in 
a  position  to  give  a  satisfactory  answer  to  this  question. 

Let  us  now  return  to  the  hydra,  the  artificial  fission  of 
which  has  suggested  these  considerations.  Multiplication 
in  this  way  is  probably  abnormal.  Under  suitable  con- 
ditions, however,  if  well  fed,  the  hydra  normally  multiplies 
by  budding.  At  some  spot,  generally  not  far  from  the 
"  foot,"  or  base  of  attachment,  a  little  swelling  occurs,  and 
the  growth  of  the  cells  in  this  region  takes  such  lines  that 
a  new  hydra  is  formed.  This  is  at  first  in  direct  con- 
nection with  the  parent  stem,  the  two  having  a  common 
internal  cavity ;  but  eventually  it  separates  and  lives  a  free 
existence  as  a  distinct  organism  (see  Fig.  9,  p.  45). 

Now,  here  we  may  notice,  as  an  implication  from  these 
facts,  that  the  size  of  the  organism  is  limited.  When  the 
normal  limits  of  size  are  reached,  any  further  assimilation 
of  nutriment  ministers,  not  to  the  further  growth  of  the 
organism,  but  to  the  formation  of  a  new  outgrowth,  or 
bud.  What  determines  that  the  outgrowth,  or  bud,  should 
originate  in  this  or  that  group  of  cells,  we  do  not  know. 
But,  like  the  isolated  fragment  in  the  hydra  subdivided 
by  fission,  the  little  group  in  which  budding  commences 
contains  a  fair  sample  of  the  various  kinds  of  cells  which 
constitute  the  hydra.  And  here,  too,  we  see  that  their 
growth  and  development  follow  definite  lines  of  hereditary 
symmetry. 


Heredity  and  the  Origin  of  Variations.     129 

But  there  is  a  third  method  of  multiplication  in  hydra  : 
this  is  the  sexual  mode  of  reproduction,  and  occurs 
generally  in  the  autumn.  On  the  body-wall  of  certain 
individuals,  near  the  tentacles,  conical  swellings  appear. 
Within  these  swellings  are  great  numbers  of  minute  sperms, 
with  small  oval  heads  and  active,  thread-like  tails.  They 
appear  to  originate  from  the  interstitial  cells  of  the  outer 
layer  (see  p.  124).  Nearer  the  foot,  or  base  of  attachment, 
and  generally,  but  not  quite  always,  in  separate  individuals, 
there  are  other  larger  swellings,  different  in  appearapce, 
of  which  there  is  generally  only  one  in  the  same  individual 
at  the  same  time.  Each  contains  a  single  ovum,  or  egg- 
cell,  surrounded  by  a  capsule.  It,  too,  and  the  cells  which 
surround  it  would  appear  to  be  developed  from  the  inter- 
stitial cells.  It  grows  rapidly  at  the  expense  of  the  sur- 
rounding tissue,  but  when  mature,  it  bursts  through  the 
enveloping  capsule,  and  is  freely  exposed.  A  sperm-cell, 
which  seems,  in  some  cases  at  least,  to  be  produced  by  the 
same  individual,  now  unites  with  it ;  the  egg-cell  then 
begins  to  undergo  division,  becomes  detached,  falls  to  the 
bottom,  and  develops  into  a  young  hydra. 

Here,  then,  we  have  that  sexual  mode  of  reproduction 
which  occurs  in  all  the  higher  animals.  It  is,  however,  in 
some  respects  peculiar  in  hydra.  In  the  first  place,  the 
ovum  is  nearly  always  in  other  animals  (but  occasionally 
not  in  hydra)  fertilized  by  the  sperm  from  a  separate  and 
distinct  individual.  In  the  second  place,  the  germinal  cells 
are  generally  produced,  not  from  the  outer  layer,  but  from 
the  middle  layer,  which  appears  between  the  two  primitive 
layers.  In  some  allies  of  hydra,  however,  they  take  their 
origin  in  the  inner  layer  ;  and  it  has  been  suggested  that, 
even  in  hydra,  the  true  germinal  cells  may  migrate  from 
the  inner  to  the  outer  layer.  But  of  this  there  does  not 
seem  to  be  at  present  sufficient  evidence.  In  any  case, 
however,  the  essential  fact  to  bear  in  mind  is  that  a  new 
individual  is  produced  by  the  union  of  a  single  cell  pro- 
duced by  one  organism  and  of  another  cell  produced  in 
most  cases  (but  not  always  in  the  hydra)  from  a  different 

K 


130  Animal  Life  and  Intelligence. 

individual.  In  the  higher  forms  of  animal  life,  the  organisms 
are  either  female  (egg-producing)  or  male  (sperm-pro- 
ducing). But  there  are  many  hermaphrodite  forms  which 
produce  both  eggs  and  sperms,  as  in  the  common  snail  and 
earthworm.  Even  in  these  cases,  however,  there  are 
generally  special  arrangements  by  which  it  is  ensured  that 
the  sperm  from  one  individual  should  fertilize  the  ovum 
produced  by  another  individual. 

What,  we  must  next  inquire,  is  the  relation  in  the  higher 
forms  of  life — for  we  may  now  leave  the  special  considera- 
tion of  hydra — of  the  ovum  or  sperm  to  the  organism  which 
produces  it  ?  This  is  but  one  mode  of  putting  a  very  old 
question — Does  the  hen  produce  the  egg,  or  does  the  egg 
produce  the  hen  ?  Of  course,  in  a  sense,  both  are  true ; 
for  the  hen  produces  an  egg  which,  if  duly  fertilized,  will 
develop  into  a  new  hen.  But  the  question  has  of  late  been 
asked  in  a  new  sense  ;  and  many  eminent  naturalists  reply, 
without  hesitation — The  egg  produces  the  hen,  but  under 
no  circumstances  does  the  hen  produce  the  egg.  What, 
then,  it  may  be  asked,  does  produce  the  egg  ?  To  this  it 
is  replied — The  egg  was  produced  by  a  previous  egg.  At 
first  sight,  this  may  seem  a  mere  quibble ;  for  it  may  be 
said  that,  of  course,  if  an  egg  produces  a  hen  which  contains 
other  eggs,  these  eggs  may  be  said  to  be  produced  by  the 
first.  But  it  is  really  more  than  a  quibble,  and  we  must  do 
our  best  clearly  to  grasp  what  is  meant. 

We  have  seen  that,  in  development,  the  fertilized  egg- 
cell  undergoes  division  into  two  cells,  each  of  which  again 
divides  into  two,  and  so  on,  again  and  again,  until  from 
one  there  arises  a  multitude  of  cells.  Nor  is  this  all.  The 
multitude  are  organized  into  a  whole.  The  constituent 
cells  have  different  forms  and  structures,  and  perform 
diverse  functions.  Some  are  skeletal,  such  as  bone  and 
connective  tissue ;  some  are  protective,  such  as  those  which 
give  rise  to  feathers  or  scales  ;  some  form  nerves  or  nerve- 
centres  ;  some,  muscles ;  some  give  rise  to  glandular  tissue ; 
and  lastly,  some  form  the  essential  elements  in  reproduc- 


Heredity  and  the  Origin  of  Variations.      131 

tion.  If,  now,  we  express  the  development  of  tissues  and 
the  sequence  of  organisms  in  the  following  scheme,  the 
continuity  of  the  reproductive  cells  will  be  apparent  :  — 


^Skeletal  and  protective  cells 

Reproductive  cell  C^^  SM^  cells 
>  cells 


Reproductive 


It  is  clear  that  there  is  a  continuity  of  reproductive 
cells,  which  does  not  obtain  with  regard  to  nerve,  gland,  or 
skeleton.  If,  then,  we  class  together  as  body-cells  those 
tissue-elements  which  constitute  what  we  ordinarily  call 
the  body,  i.e.  the  head,  trunk,  limbs — all,  in  fact,  except  the 
reproductive  cells,  our  scheme  becomes — 

Reproductive  ceUO—^ductive  cells    O^froductive  cells    O— £ 

From  this,  again,  it  is  clear  that  the  body  does  not  pro- 
duce the  egg,  or  reproductive  cell,  but  that  the  reproductive 
cell  does  produce  the  body.  Of  course,  it  should  be  noted 
that  we  are  here  using  the  term  "  body  "  as  distinguished 
from,  and  not  as  including,  the  reproductive  cells.  But  this 
is  convenient,  in  that  it  emphasizes  the  fact  that  the  mus- 
cular, nervous,  skeletal,  and  glandular  cells  take  (on  this 
view)  no  part  whatever  in  producing  those  reproductive 
cells  which  are  concerned  in  the  continuance  of  the  species. 

Such,  in  brief,  is  the  view  that  the  egg  produces  the 
hen.  We  will  return  to  it  presently  when  we  have  glanced 
at  the  alternative  view  that  the  hen  produces  the  egg. 

On  this  view,  the  reproductive  elements  are.  not  merely 
cells,  the  result  of  normal  cell-division,  which  have  been 
set  aside  for  the  continuance  of  the  species.  They  are,  so 
to  speak,  the  concentrated  extract  of  the  body,  and  con- 
tain minute  or  infinitesimal  elements  derived  from  all  the 
different  tissues  of  the  organism  which  produces  them. 
Darwin  *  suggested  that  all  the  cells  of  the  various  tissues 
produce  minute  particles  called  gemmules,  which  circulate 

*  Darwin,  "  Animals  and  Plants  under  Domestication,"  2nd  edit.,  vol.  ii. 
chap,  xxvii.,  from  which  the  following  description  and  quotations  are  taken. 


132  Animal  Life  and  Intelligence. 

freely  throughout  the  body,  but  eventually  find  a  home  in 
the  reproductive  cells.  Just  as  the  organism  produces  an 
ovum  from  which  an  organism  like  itself  develops,  so  do 
the  cells  of  the  organism  produce  gernmules,  which  find 
their  way  to  the  ovum  and  become  the  germs  of  similar 
cells  in  the  developing  embryo.  "  The  child,  strictly 
speaking,"  says  Darwin,  "  does  not  grow  into  a  man,  but 
includes  germs  which  slowly  and  successively  become 
developed  and  form  the  man."  "Each  animal  may  be 
compared  with  a  bed  of  soil  full  of  seeds,  some  of  which 
soon  germinate,  some  lie  dormant  for  a  period,  whilst 
others  perish."  Or,  to  vary  the  analogy,  "an  organic 
being  is  a  microcosm — a  little  universe  formed  of  a  host 
of  self-propagating  organisms."  This  is  Darwin's  pro- 
visional hypothesis  of  pangenesis,  which  has  recently  been 
accepted  in  a  modified  form  by  Professor  W.  K.  Brooks  in 
America,  to  some  extent  by  De  Vries  on  the  Continent,  by 
Professor  Herdman  of  Liverpool,  and  by  other  biologists. 
The  ovum  on  this  view  is  to  be  regarded  as  a  composite 
germ  containing  the  germs  of  the  cellular  constituents  of 
the  future  organism.  The  scheme  representing  this  view 
will  stand  thus — 

Skeletal  and  protective  cells  ^_     ^.  »k.  and  pr.  ^^    ^  8. 

Reproductive  cell  O Nerve  and  muscle  fells  "^^O n-  an^  m-  ^^O ' —  n- 

^~-_Glandular  and  nutritive  cells  ^"^      ^  gl.  and  nu.  '•""      ~^-~-  gl. 

It  is  clear  that,  on  this  hypothesis,  we  may  frame  an 
apparently  simple  and,  on  first  sight,  satisfactory  theory  of 
heredity.  Since  all  the .  body-cells  produce  gemmules, 
which  collect  in  or  give  rise  to  the  reproductive  cells,  and 
since  each  gemmule  is  the  germ  of  a  similar  cell,  what  can 
be  more  natural  than  that  the  ovum,  thus  composed  of 
representative  cell-germs,  should  develop  into  an  organism 
resembling  the  parent  organism  ?  Modifications  of  structure 
acquired  during  the  life  of  the  organism  would  thus  be 
transmitted  from  parent  to  offspring ;  for  the  modified  cells 
of  the  parent  would  give  rise  to  modified  gemmules,  which 
would  thus  hand  on  the  modification.  The  inheritance  of 
ancestral  traits  from  grandparent  or  great-grandparent 
might  be  accounted  for  by  supposing  that  some  of  the 


Heredity  and  the  Origin  of  Variations.     133 

gemmules  remained  latent  to  develop  in  the  second  or 
third  generation.  The  regeneration  of  lost  parts  receives 
also  a  ready  explanation.  If  a  part  be  removed  by  ampu- 
tation, regrowth  is  possible  because  there  are  disseminated 
throughout  the  body  gemmules  derived  from  each  part  and 
from  every  organ.  A  stock  of  nascent  cells  or  of  partially 
developed  gemmules  may  even  be  retained  for  this  special 
purpose,  either  locally  or  throughout  the  body,  ready  to 
combine  with  the  gemmules  derived  from  the  cells  which 
come  next  in  due  succession.  Similarly,  in  budding,  the 
buds  may  contain  nascent  cells  or  gemmules  in  a  some- 
what advanced  stage  of  development,  thus  obviating  the 
necessity  of  going  through  all  the  early  stages  in  the 
genesis  of  tissues.  The  gemmules  derived  from  each  part 
being,  moreover,  thoroughly  dispersed  through  the  system, 
a  little  fragment  of  such  an  organism  as  hydra  may  con- 
tain sufficient  to  rebuild  the  complete  organism ;  or,  if  it 
contains  an  insufficient  number,  we  may  assume  that  the 
gemmules,  in  their  undeveloped  state,  are  capable  of  multi- 
plying indefinitely  by  self-division.  Finally,  variations 
might  arise  from  the  superabundance  of  certain  gemmules 
and  the  deficiency  of  others,  and  from  the  varying  potency 
of  the  gemmules  contained  in  the  sperm  and  ovum.  Where 
the  maternal  and  paternal  gemmules  are  of  equal  potency, 
the  cell  resulting  from  their  union  will  be  a  true  mean 
between  them  ;  where  one  or  other  is  prepotent,  the  result- 
ing cell  will  tend  in  a  corresponding  direction.  And  since 
the  parental  cells  are  subject  to  modification,  transmitted 
through  the  gemmules  to  the  reproductive  elements,  it  is 
clear  that  there  is  abundant  room  and  opportunity  for 
varietal  combinations. 

It  is  claimed,  as  one  of  the  chief  advantages  of  some 
form  of  pangenetic  hypothesis,  that  it,  and  it  alone,  enables 
us  to  explain  the  inheritance  of  characters  or  modifications 
of  structure  acquired  by  use  (or  lost  by  disuse)  during  the 
life  of  the  organism,  or  imprinted  on  the  tissues  by  en- 
vironmental stresses.  The  evidence  for  the  transmission 
of  such  acquired  characters  we  shall  have  to  consider 


134  Animal  Life  and  Intelligence. 

hereafter.  We  may  here  notice,  however,  that  at  first 
sight  the  hypothesis  seems  to  prove  too  little  or  too  much. 
For  while  modifications  of  tissues,  the  effects  of  use  and 
disuse,  are  said  to  be  inherited,  the  total  removal  of  tissues 
by  amputation,  even  if  repeated  generation  after  generation, 
as  in  the  docking  of  the  tails  of  dogs  and  horses,  formerly 
so  common,  does  not  have  the  effect  of  producing  offspring 
similarly  modified.  Professor  Weismann  has  recently 
amputated  the  tails  of  white  mice  so  soon  as  they  were 
born,  for  a  number  of  generations,  but  there  is  no  curtail- 
ment of  this  organ  in  the  mice  born  of  parents  who  had 
not  only  themselves  suffered  in  this  way,  but  whose 
parents,  grandparents,  and  great-grandparents  were  all 
rendered  tailless.  The  pangenetic  answer  to  this  objection 
is  that  gemmules  multiply  and  are  transmitted  during 
long  series  of  generations.  We  have  only  to  suppose  that 
the  gemmules  of  distantly  ancestral  tails  have  been  passing 
through  the  mutilated  mice  in  a  dormant  condition,  await- 
ing an  opportunity  to  develop,  and  the  constant  reappear- 
ance of  tails  is  seen  to  be  no  real  anomaly.  In  this  case 
the  gemmules  of  the  parental  and  grandparental  tail  are 
simply  absent.  But  if  the  muscles  of  the  parental  tail 
were  modified  through  unwonted  use,  the  modified  cells 
would  give  rise  to  modified  gemmules,  which  would  unite 
in  generation  with  ancestral  gemmules,  and  to  a  greater 
or  less  degree  modify  them.  The  difference  is  between  the 
mere  absence  of  gemmules  and  the  presence  of  modified 
gemmules.  And  the  fact  that  it  takes  some  generations 
for  the  effects  of  use  or  disuse  to  become  marked  is 
(pangenetically)  due  to  the  fact  that  it  takes  some  time  for 
the  modified  gemmules  to  accumulate  and  be  transmitted 
in  sufficient  numbers  to  affect  seriously  the  numerous 
ancestral  gemmules. 

The  direction  in  which  Professor  W.  K.  Brooks  has 
recently  sought  to  modify  Darwin's  pangenetic  hypothesis 
may  here  be  briefly  indicated.  He  holds  that  it  is  under 
unwonted  and  abnormal  conditions  that  the  cells  are 
stimulated  to  produce  gemmules,  and  that  the  sperm  is 


Heredity  and  the  Origin  of  Variations.     135 

the  special  centre  of  their  accumulation.  '  Hence  it  is  the 
paternal  influence  which  makes  for  variation,  the  maternal 
tendency  being  conservative.  The  reproductive  cell  is  not 
merely  or  chiefly  a  microcosm  of  gemmules.  It  is  a  cell 
produced  by  ordinary  cell- division  from  other  reproductive 
cells.  The  ovum  remains  comparatively  unaffected  by 
changes  in  the  body ;  but  it  receives  from  the  sperm,  with 
which  it  unites,  gemmules  from  such  tissues  in  the  male 
as  were  undergoing  special  modification.  The  hen  does 
not  produce  the  egg;  but  the  cock  does  produce  the  sperm ; 
and  the  union  of  the  two  hits  the  happy  mean  between  the 
conservatism  of  the  one  view  and  the  progressive  possi- 
bilities of  the  other. 

Mr.  Francis  Galton,  in  1876,*  suggested  a  modification 
of  Darwin's  hypothesis,  which  included,  as  does  that  of 
Professor  Brooks,  the  idea  of  germinal  continuity  which 
had  been  suggested  by  Professor  (now  Sir  Kichard)  Owen, 
in  1849.  He  calls  the  collection  of  gemmules  in  the 
fertilized  ovum  the  "  stirp."  Of  the  gemmules  which  con- 
stitute the  stirp  only  a  certain  number,  and  they  the  most 
dominant,  develop  into  the  body-cells  of  the  embryo.  The 
rest  are  retained  unaltered  to  form  the  germinal  cells  and 
keep  up  a  continuous  tradition.  Mr.  Galton's  place  in  the 
history  of  theories  of  heredity  can  scarcely  be  placed  too 
high.  Only  one  further  modification  of  pangenesis  can 
here  be  mentioned,  namely,  that  proposed  in  1883  by 
Professor  Herdman,  of  Liverpool.  He  suggested  "  that  the 
body  of  the  individual  is  formed,  not  by  the  development 
of  gemmules  alone  and  independently  into  cells,  but  by  the 
gemmules  in  the  cells  causing,  by  their  affinities  and 
repulsions,  these  cells  so  to  divide  as  to  give  rise  to  new 
cells,  tissues,  and  organs." 

Such  are  Darwin's  provisional  hypothesis  of  pangenesis, 
and  some  more  recent  modifications  thereof.  Bold  and 
ingenious  as  was  Darwin's  speculation,  supported  as  it  at 

*  For  an  excellent  account  of  the  genesis  and  growth  of  the  modern  views 
of  heredity,  see  Mr.  J.  Arthur  Thomson's  paper  on  "The  History  and  Theory 
of  Heredity  :  "  Proceedings  of  the  Royal  Society  of  Edinburgh,  1889. 


136  Animal  Life  and  Intelligence. 

first  sight  seems  to  be  by  organic  analogies,  it  finds  to-day 
but  few  adherents.  With  all  our  increased  modern  micro- 
scopical appliances,  no  one  has  ever  seen  the  production 
of  gemmules.  Although  it  appears  sufficiently  logical  to 
say  that,  just  as  a  large  organism  produces  a  small  ovum, 
so  does  each  small  cell  produce  an  exceedingly  minute 
gemmule ;  when  closely  investigated,  the  analogy  is  not 
altogether  satisfactory.  It  is  denied,  as  we  have  seen,  by 
many  biologists  that  the  organism  does  produce  the  ovum. 
Multiplication  is  normally  by  definite,  visible  cell-division. 
Nuclear  fission  can  be  followed  in  all  its  phases.  But 
where  is  the  nuclear  fission  in  the  formation  of  gemmules  ? 
It  is  true  that  the  conjugation  of  monads  is  followed  by 
the  pouring  forth  of  a  fluid  which  must  be  crowded  with 
germs  from  which  new  monads  arise,  and  that  these  germs 
are  so  minute  as  to  be  invisible,  even  under  high  powers 
of  the  microscope.  It  might  be  suggested,  then,  that  in 
every  tissue  some  typical  cell  or  cells  might  thus  break  up 
into  a  multitude  of  invisible  gemmules.  But  there  is  at 
present  no  evidence  that  they  do  so.  And  even  if  this  were 
the  case,  it  would  not  bear  out  Darwin's  view,  that  every 
cell  is  constantly  throwing  off  numerous  gemmules.  It  is 
known,  however,  or  at  least  generally  believed,  that  there 
is  a  constant  replacement  of  tissues  during  the  life  of  the 
organism.  It  is  said,  for  example,  that  in  the  course  of 
seven  years  the  whole  cellular  substance  of  the  human 
body  is  entirely  renewed.  The  fact  is,  I  think,  open  to 
question.  Granting  it,  however,  it  might  be  suggested 
that  the  effete  cells,  ere  they  vanish,  give  rise  to  minute 
gemmules,  which  find  their  way  to  the  ova.  But  it  must 
be  remembered  that  the  new  tissue-cells  in  the  supposed 
successional  renewal  of  the  organs  are  the  descendants  of 
the  old  tissue-cells ;  that  these  are,  therefore,  already 
reproducing  their  kind  directly ;  and  that  the  formation  of 
gemmules  would  thus  be  a  special  superadded  provision 
for  a  future  generation.  Still,  there  is  no  reason  why  cells 
should  not  have  this  double  mode  of  reproduction,  if  any 
definite  evidence  of  its  existence  could  be  brought  forward. 


Heredity  and  the  Origin  of  Variations.      137 

Without  such  definite  evidence,  we  may  well  hesitate  before 
we  accept  it  even  provisionally. 

The  existence  of  gemmules,  then,  is  unproven,  and  their 
supposed  mode  of  origin  not  in  altogether  satisfactory 
accordance  with  organic  analogies.  Furthermore,  the 
whole  machinery  of  the  scheme  of  heredity  is  complicated 
and  hyper-hypothetical.  It  is  difficult  to  read  Darwin's 
account  of  reversion,  the  inheritance  of  functionally 
acquired  characters,  and  the  non-inheritance  of  mutilation, 
or  to  follow  his  skilful  manipulation  of  the  invisible  army 
of  gemmules,  without  being  tempted  to  exclaim — What 
cannot  be  explained,  if  this  be  explanation  ?  and  to  ask 
whether  an  honest  confession  of  ignorance,  of  which  we 
are  all  so  terribly  afraid,  be  not,  after  all,  a  more  satis- 
factory position. 

That  the  hen  produces  the  egg,  that  "gemmules  are 
collected  from  all  parts  of  the  system  to  constitute  the 
sexual  elements,  and  that  their  development  in  the  next 
generation  forms  a  new  being,"  is  further  rendered  im- 
probable by  direct  observation  upon  the  mode  of  origin  of 
the  germinal  cells,  ova,  or  sperms. 

It  will  be  remembered  that  the  view  that  the  egg 
produces  the  hen,  while  the  hen  does  not  produce  the  egg, 
suggested  the  question — What,  then,  does  produce  the 
egg?  to  which  the  answer  was — The  egg  is  the  product 
of  a  previous  egg.  On  this  view,  then,  the  germinal  cells, 
ova,  or  sperms  are  the  direct  and  unmodified  descendants 
of  an  ovum  and  sperm  which  have  entered  into  fertile 
union.  Now,  in  certain  cases,  notably  in  the  fly  Chironomus, 
studied  by  Professor  Balbiani,  but  also  in  a  less  degree 
in  some  other  invertebrate  forms,  it  is  possible  to  trace  the 
continuity  of  the  germinal  cells  with  the  fertilized  ovum 
from  which  they  are  derived.  In  Chironomus,  for  example, 
"  at  a  very  early  stage  in  the  embryo,  the  future  reproduc- 
tive cells  are  distinguishable  and  separable  from  the  body- 
forming  cells.  The  latter  develop  in  manifold  variety,  into 
skin  and  nerve,  muscle  and  blood,  gut  and  gland;  they 
differentiate,  and  lose  almost  all  protoplasmic  likeness  to 


138  Animal  Life  and  Intelligence. 

the  mother  ovum.  But  the  reproductive  cells  are  set  apart ; 
they  take  no  share  in  the  differentiation,  but  remain 
virtually  unchanged,  and  continue  unaltered  the  proto- 
plasmic tradition  of  the  original  ovum."*  In  such  a  case, 
then,  observation  flatly  negatives  the  view  that  the  germinal 
cells  are  "constituted"  by  gemmules  collected  from  the 
body-cells,  though,  of  course  (on  a  modified  pangenetic 
hypothesis),  they  might  be  the  recipients  of  such  gemmules. 

It  is  only  in  a  minority  of  cases,  however,  that  the  direct 
continuity  of  germinal  cells  as  such  is  actually  demonstrable. 
In  the  higher  vertebrates,  for  instance,  the  future  repro- 
ductive cells  can  first  be  recognized  only  after  differentiation 
of  some  of  the  body-cells  and  the  tissues  they  constitute 
is  relatively  advanced.  While  in  cases  of  alternation  of 
generations,  "  an  entire  asexual  generation,  or  more  than 
one,  may  intervene  between  one  ovum  and  another."  In 
all  such  cases  the  continuity  of  the  chain  of  recognizably 
germinal  cells  cannot  be  actually  demonstrated. 

The  impracticability  of  actually  demonstrating  a  con- 
tinuity of  germinal  cells  in  the  majority  of  cases  has 
induced  Professor  Weismann  to  abandon  the  view  that 
there  is  a  continuity  of  germinal  cells,  and  to  substitute 
for  it  the  view  that  there  is  a  continuity  of  germ-plasm 
(keimplasma) .  "A  continuity  of  germ-cells,"  he  says,t 
"does  not  now  take  place,  except  in  very  rare  instances; 
but  this  fact  does  not  prevent  us  from  adopting  a  theory  of 
the  continuity  of  the  germ-plasm,  in  favour  of  which  much 
weighty  evidence  can  be  brought  forward."  It  might, 
however,  be  suggested  that,  although  a  continuity  of 
germ-cells  cannot  be  demonstrated,  such  continuity  may, 
nevertheless,  obtain,  the  future  germinal  cells  remaining 
undifferentiated,  while  the  cells  around  them  are  under- 
going differentiation.  The  comparatively  slight  differentia- 
tion of  the  body-cells  in  hydroids  renders  such  a  view  by 
no  means  improbable.  But  Professor  Weismann  does  not 
regard  such  an  idea  as  admissible,  at  all  events,  in  certain 

*  Geddea  and  Thomson,  "The  Evolution  of  Sex,"  p.  92. 

t  Weisuiann,  "  Essays  on  Heredity,"  English  translation,  p.  173. 


Heredity  and  the  Origin  of  Variations.      1 39 

cases.  "It  is  quite  impossible,"  he  says,*  "to  maintain 
that  the  germ-cells  of  hydroids,  or  of  the  higher  plants, 
exist  from  the  time  of  embryonic  development,  as  undif- 
ferentiated  cells,  which  cannot  be  distinguished  from 
others,  and  which  are  only  differentiated  at  a  later  period." 
The  number  of  daughter-cells  in  a  colony  of  hydroid 
zoophytes  is  so  great  that  "all  the  cells  of  the  embryo 
must  for  a  long  time  act  as  body-cells,  and  nothing  else." 
Moreover,  actual  observation  (e.g.  in  Coryne)  convinces  Dr. 
Weismann  that  ordinary  body-cells  are  converted  into 
reproductive  cells.  After  describing  the  parts  of  the  body- 
wall  in  which  a  sexual  bud  arises  as  in  no  way  different 
from  surrounding  areas,  he  says,  "Bapid  growth,  then, 
takes  place  at  a  single  spot,  and  some  of  the  young  cells 
thus  produced  are  transformed  into  germ-cells  which  did  not 
previously  exist  as  separate  cells. "f 

This  transformation  of  body-cells  or  their  daughter- 
cells  into  germ-cells  seems  therefore,  if  it  be  admitted,  to 
negative  the  continuity  of  germ-cells  as  such.  But  this 
fact,  says  Weismann,  does  not  prevent  us  from  adopting  a 
theory  of  the  continuity  of  germ-plasm.  "As  a  result  of 
my  investigations  on. hydroids,"  he  says,J  "I  concluded 
that  the  germ-plasm  is  present  in  a  very  finely  divided 
and  therefore  invisible  state  in  certain  body-cells,  from 
the  very  beginning  of  embryonic  development,  and  that  it 
is  then  transmitted,  through  innumerable  cell-generations, 
to  those  remote  individuals  of  the  colony  in  which  the 
sexual  products  are  formed." 

This_germ-pla^m_ resides  in  the  nucleus  of  the  cell; 
and  it  would  seem  that  by  a  little  skilful  manipulation  it 

*  Weismann,  "  Essays  on  Heredity,"  p.  205. 

t  A  few  pages  earlier  (p.  200)  in  the  same  essay,  Professor  Weismann 
says,  "A  sudden  transformation  of  the  nucleo-plasm  of  a  somatic  cell  into 
that  of  a  germ-cell  would  be  almost  as  incredible  as  the  transformation  of  a 
mammal  into  an  amoeba."  This  at  first  sight  does  not  seem  quite  consistent 
with  the  subsequent  sentence  which  I  have  quoted  in  the  text;  for  here,  at 
any  rate,  the  daughters  of  "  mammals  "  are  said  to  be  converted  into  "  amoebae." 
But  this  is  no  doubt  because  the  amoebse  (germ-plasms)  are  contained  in  the 
mammals  (body-cells).  (See  the  quotations  that  follow  in  the  text.) 

J  Weismann,  "  Essays  on  Heredity,"  p.  207. 


I4O  Animal  Life  and  Intelligence. 

can  be  made  to  account  for  anything  that  has  ever  been 
observed  or  is  ever  likely  to  be  observed.  It  is  one  of 
those  convenient  invisibles  that  will  do  anything  you 
desire.  The  regrowth  of  a  limb  shows  that  the  cells  con- 
tained some  of  the  original  germ- plasm.  A  little  sampled 
fragment  of  hydra  has  it  in  abundance.  It  lurks  in  the 
body- wall  of  the  budding  polype.  It  is  ever  ready  at  call. 
It  conveniently  accounts  for  atavism,  or  reversion;  for* 
"  the  germ-plasm  of  very  remote  ancestors  can  occasionally 
make  itself  felt.  Even  a  very  minute  trace  of  a  specific 
germ-plasm  possesses  the  definite  tendency  to  build  up  a 
certain  organism,  and  will  develop  this  tendency  as  soon 
as  the  nutrition  is,  for  some  reason,  favoured  above  that  of 
the  other  kinds  of  germ-plasm  present  in  the  nucleus." 

In  place,  then,  of  the  direct  continuity  of  germ-cells  as 
distinct  from  body-cells,  we  have  here  the  direct  continuity 
of  germ-plasm  as  opposed  to  body-plasm.  The  germ-plasm 
can  give  rise  to  body-plasm  to  any  extent ;  the  body-plasm 
can  never  give  rise  to  germ-plasm.  If  it  seems  to  do  so, 
this  is  only  because  the  nuclei  of  the  body-cells  contain 
some  germ-plasm  in  an  invisible  form.  The  body-plasm 
dies ;  but  the  life  of  the  germ-plasm  is,  under  appropriate 
conditions,  indefinitely  continuous. 

So  far  as  heredity  is  concerned,  it  matters  not  whether 
there  be  a  continuity  of  germ-cells  or  of  germ-plasma.  In 
either  case,  the  essential  feature  is  that  body-cells  as  such 
cannot  give  rise  to  the  germ — that  the  hen  cannot  produce 
the  egg.  On  either  view,  characters  acquired  by  the  body 
cannot  be  transmitted  to  the  offspring  through  the  ova  or 
sperms.  The  annexed  diagram  illustrates  how,  on  the 
view  that  the  hen  produces  the  egg,  dints  hammered  into 
the  body  by  the  environment  will  be  handed  on ;  while,  on 
the  view  that  the  hen  does  not  produce  the  egg,  the  dints 
of  the  environment  are  not  transmitted  to  the  offspring. 
On  the  hypothesis  of  continuity,  heredity  is  due  to  the  fact 
that  two  similar  things  under  similar  conditions  will  give 
similar  products.  The  ovum  from  which  the  mother  is 
*  Weismann,  "  Essays  on  Heredity,"  p.  179. 


Heredity  and  the  Origin  of  Variations.      141 

developed,  and  the  ovum  from  which  the  daughter  is 
developed,  are  simply  two  fragments  separated  at  different 
times  from  the  same  continuous  germ-plasm.*  Both 
develop  under  similar  circumstances,  and  their  products 
cannot,  therefore,  fail  to  be  similar.  How  variation  is 
possible  under  these  conditions  we  shall  have  to  consider 
presently. 

Now,  although  I  value  highly  Professor  "Weismann's 


n. 

Fig.  21.— Egg  and  hen. 

7.  "  The  egg  produces  the  hen."  II.  "  The  hen  produces  the  egg."  In  /.  the  dints  pro- 
duced by  the  environment  are  not  inherited  ;  in  //.  they  are.  The  letters  indicate  successive 
individuals.  The  small  round  circles  indicate  the  eggs. 

luminous  researches,  and  read  with  interest  his  ingenious 
speculations,  I  cannot  but  regard  his  doctrine  of  the  con- 
tinuity of  germ-plasm  as  a  distinctly  retrograde  step.  His 
germ-plasm  is  an  unknowable,  invisible,  hypothetical  entity. 
Material  though  it  be,  it  is  of  no  more  practical  value  than 
a  mysterious  and  mythical  germinal  principle.  By  a  little 
skilful  manipulation,  it  may  be  made  to  account  for  any- 

*  It  will,  of  course,  be  understood  that  a  minute  fragment  of  germ-plasm 
is  capable  of  almost  unlimited  growth  by  assimilation  of  nutritive  material, 
its  properties  remaining  unchanged  during  such  growth. 


142  Animal  Life  and  Intelligence. 

thing  and  everything.  The  fundamental  assumption  that 
whereas  germ-plasm  can  give  rise  to  body-plasm  to  any 
extent,  body-plasm  can  under  no  circumstances  give  rise  to 
germ-plasm,  introduces  an  unnecessary  mystery.  Biological 
science  should  set  its  face  against  such  mysteries.  The 
fiction  of  two  protoplasms,  distinct  and  yet  commingled, 
is,  in  my  opinion,  little  calculated  to  advance  our  know- 
ledge and  comprehension  of  organic  processes.  For  myself, 
I  prefer  to  take  my  stand  on  protoplasmic  unity  and 
cellular  continuity.  ^-a^T' 

The  hypothesis  of  cellular  continuity  is  ^me  that  the 
researches  of  embryologists  tend  more  and  more  to  justify. 
The  fertilized  ovum  divides  and  subdivides,  and,  by  a  con- 
tinuance of  such  processes  of  subdivision,  gives  rise  to  all 
the  cells  of  which  the  adult  organism  is  composed.  It  is 
true  that  in  some  cases,  as  in  that  of  peripatus,  as  inter- 
preted by  Mr.  Adam  Sedgwick,  the  cells  of  the  embryo  run 
together  or  remain  continuous  as  a  diffused  protoplasmic 
mass  with  several  or  many  nuclei.  But  this  seemingly 
occurs  only  in  early  stages  as  a  step  towards  the  separation 
of  distinct  cells.  And  even  if  the  process  should  be  proved 
of  far  wider  occurrence,  it  would  not  disprove  the  essential 
doctrine  of  cellular  continuity.  The  nucleus  is  the  essence 
of  the  cell.  And  the  doctrine  of  cellular  continuity  empha- 
sizes the  fact  that  the  nuclei  of  all  the  cells  of  the  body 
are  derived  by  a  process  of  divisional  growth  from  the  first 
segmentation-nucleus  which  results  from  the  union  of  the 
nuclei  of  the  ovum  and  the  sperm.  In  this  sense,  then, 
however  late  the  germinal  cells  appear  as  such,  they  are 
in  direct  continuity  with  the  germinal  cell  from  which 
they,  in  common  with  all  the  cells  of  the  organism,  derive 
their  origin.  In  this  sense  there  is  a  true  continuity  of 
germ- cells. 

Now,  it  has  again  and  again  been  pointed  out  that  the 
simple  cell  of  which  an  amoeba  is  composed  is  able  to  per- 
form, in  simple  fashion,  the  various  protoplasmic  functions. 
It  absorbs  and  assimilates  food ;  it  is  contractile  and 
responds  to  stimulation ;  it  respires  and  exhibits  metabolic 


Heredity  and  the  Origin  of  Variations.     143 

processes;  it  undergoes  fission  and  is  reproductive.  The 
metazoa  are  cell-aggregates ;  and  in  them  the  cells 
exemplify  a  physiological  division  of  labour.  They  dif- 
ferentiate, and  give  rise  to  muscle  and  nerve,  gut  and 
gland,  blood  and  connective  or  skeletal  tissue,  ova  and 
sperms.  Are  these  germinal  cells  mysteriously  different 
from  all  the  other  cells  which  have  undergone  differentia- 
tion ?  No.  They  are  the  cells  which  have  been  differentiated 
and  set  apart  for  the  special  work  of  reproduction,  as  others 
have  been  differentiated  and  set  apart  for  other  protoplasmic 
functions. 

Cell-reproduction  is,  however,  in  the  metazoa  of  tw< 
kinds.     There  is  the  direct  reproduction  of  differentiate 
cells,  by  which  muscle-cells,  nerve-cells,  or  others  reprodm 
their  kind  in  the  growth  of  tissues  or  organs ;  and  there 
is  the  developmental  reproduction,  by  which  the  germinal 
cells  under  appropriate  conditions  reproduce  an  organism   } 
similar  to  the  parent.     The  former  is  in  the  direct  line  of\ 
descent   from  the   simple  reproduction  of  amceba.     The 
latter  is  something  peculiarly  metazoan,  and  is,  if  one 
may  be  allowed  the  expression,  specialized  in  its  generality. 

That  the  metazoa  are  derived  from  the  protozoa  is 
generally  believed.  How  they  were  developed  is  to  a  large 
extent  a  matter  of  speculation.  But,  however  originating, 
their  evolution  involved  the  production,  from  cells  of  one 
kind,  of  cells  of  two  or  more  kinds,  co-operating  in  the 
same  organism.  Whenever  and  however  this  occurred,  the 
new  phase  of  developmental  reproduction  must  have  had 
its  origin.  And  if  in  cell-division  there  is  any  continuity 
of  protoplasmic  power,  the  faculty  of  producing  diverse 
co-operating  cells  would  be  transmitted.  On  any  view  of 
the  origin  of  the  metazoa,  this  diverse  or  developmental 
reproduction  is  a  new  protoplasmic  faculty ;  on  any  view, 
it  must  have  been  transmitted,  for  otherwise  the  metazoa 
would  have  ceased  to  exist.  This  new  faculty  of  develop- 
mental reproduction,  then,  with  the  inception  of  the  metazoa, 
takes  its  place  among  other  protoplasmic  faculties,  and, 
with  the  progress  of  differentiation  and  the  division  of 


144  Animal  Life  and  Intelligence. 

labour,  will  become  the  special  business  of  certain  cells. 
On  this  view,  the  specialization  of  the  reproductive  faculty 
and  of  germinal  cells  takes  its  place  in  line  with  other  cell- 
differentiations  with  division  of  labour  ;  and  the  difficulties 
of  comprehending  and  following  the  process  of  differentia- 
tion in  this  matter  are  similar  to  those  which  attend 
physiological  division  of  labour  in  general. 

It  is  probable  that,  in  the  lower  metazoa,  in  which 
differentiation  has  not  become  excessively  stereotyped,  the 
power  of  developmental  reproduction  is  retained  by  a  great 
number  of  cells,  even  while  it  is  being  specialized  in  certain 
cells.  Hence  the  ability  to  produce  lost  parts  and  the 
reproduction  of  hydra  by  fission.  But,  on  the  other  hand, 
the  special  differentiation  of  a  tissue  on  particular  lines 
has  always  a  tendency  to  disqualify  the  cells  from  perform- 
ing other  protoplasmic  faculties,  and  that  of  developmental 
reproduction  among  the  number.  I  do  not  know  of  any 
definite,  well-observed  cases  on  record  in  the  animal  kingdom 
of  ova  or  sperms  being  derived  from  cells  which  are  highly 
differentiated  in  any  other  respect.  In  the  vertebrata,  the 
mesoblastic,  or  mid-layer,  cells,  from  which  the  germinal 
epithelium  arises,  have  certainly  not  been  previously 
differentiated  in  any  other  line.  And  in  the  case  of  the 
hydroid  zoophytes,  quoted  by  Professor  Weismann,  the 
cells  which  give  rise  to  the  germinal  products  have  never 
been  so  highly  differentiated  as  to  lose  the  protoplasmic 
faculty  of  developmental  reproduction. 

Some  such  view  of  developmental  reproduction,  based 
upon  cellular  continuity  and  the  division  of  labour,  seems 
to  me  more  in  accord  with  the  general  teachings  of  modern 
biology  than  a  hypothetical  and  arbitrary  distinction 
between  a  supposed  germ-plasm  and  a  supposed  body- 
plasm. 

To  which  category,  then,  does  this  hypothesis  belong  ? 
Does  it  support  the  view  that  the  hen  produces  the  egg  or 
that  the  egg  produces  the  hen  ?  Undoubtedly  the  latter. 
It  is  based  on  cellular  continuity,  and  is  summarized  by  the 
scheme  on  p.  181.  It  adequately  accounts  for  hereditary 


Heredity  and  the  Origin  of  Variations.      145 

continuity,  for  there  is  a  continuity  of  the  germinal  cells, 
the  bearers  of  heredity.  But  how,  it  may  be  asked,  on 
this  view,  or  on  any  continuity  hypothesis,  are  the  origin 
of  variations  and  their  transmission  to  be  accounted  for  ? 
To  this  question  we  have  next  to  turn.  But  before  doing 
so,  it  will  be  well  to  recapitulate  and  summarize  the  positions 
we  have  so  far  considered. 

We  saw  at  the  outset  that  the  facts  we  have  to  account 
for  are  those  of  heredity  with  variation.  To  lead  up  to  the 
facts  of  sexual  heredity,  we  considered  fission,  the  regenera- 
tion of  lost  parts,  and  budding  in  the  lower  animals.  We 
saw  that,  if  a  hydra  be  divided,  each  portion  reproduces 
appropriately  the  absent  parts.  But  we  found  it  difficult 
to  say  whether  this  power  resides,  in  such  cases,  in  the 
cells  along  the  plane  of  section  or  in  the  general  mass  of 
cells  which  constitute  the  regenerating  portion. 

Having  led  up  to  the  sexual  mode  of  reproduction,  we 
inquired  whether  the  egg  produces  the  hen  or  the  hen  pro- 
duces the  egg.  We  saw  that  there  is  a  marked  difference 
between  a  direct  continuity  of  reproductive  cells,  giving  rise 
to  body-cells  as  by-products,  and  an  indirect  continuity  of 
reproductive  cells,  these  cells  giving  rise  to  the  hen,  and 
then  the  hen  to  fresh  reproductive  cells,  which,  on  this 
view,  are  to  be  regarded  as  concentrated  essence  of  hen. 

Darwin's  hypothesis  of  pangenesis  as  exemplifying  the 
latter  view  was  considered  at  some  length,  and  the  modi- 
fications suggested  by  Professor  Brooks,  Mr.  Galton,  and 
Professor  Herdman  were  indicated.  The  hypothesis,  so  far 
as  it  is  regarded  as  a  theory  of  the  main  facts  of  heredity, 
was  rejected. 

It  was  then  pointed  out  that  only  in  a  few  cases  has  a 
direct  continuity  of  germinal  cells  as  such  been  actually 
demonstrated.  Whence  Professor  Weismann  has  been  led 
to  elaborate  his  doctrine  of  the  continuity  of  germ-plasm. 
This  germ-plasm  can  give  rise  to,  but  cannot  originate 
from,  body-plasm.  It  may  lurk  in  body-cells,  which  may, 
by  its  subsequent  development,  be  transformed  into  germ- 
cells.  But  any  external  influences  which  may  affect  these 

L 


146  Animal  Life  and  Intelligence, 

body-cells  produce  no  change  on  the  germ-plasm  which  they 
may  contain.  We  regarded  this  hypothesis  as  a  retrograde 
step,  much  as  we  admire  the  genius  of  its  propounder,  and 
considered  that  the  fiction  of  two  protoplasms,  distinct  and 
yet  commingled,  is  little  calculated  to  advance  our  com- 
prehension of  organic  processes. 

In  the  known  and  observed  phenomena  of  cellular  con- 
tinuity and  cell-differentiation,  we  found  a  sufficiently  satis- 
factory hypothesis  of  heredity.  The  reproductive  cells 
are  the  outcome  of  normal  cell-division,  and  have  been 
differentiated  and  set  apart  for  the  special  work  of  develop- 
mental reproduction,  as  others  have  been  differentiated 
and  set  apart  for  other  protoplasmic  functions.  Such  a 
view  adequately  accounts  for  hereditary  continuity,  for 
there  is  a  continuity  of  the  germinal  cells,  the  bearers  of 
heredity.  But  how,  we  repeat,  on  this  view  or  any  other 
hypothesis  of  direct  continuity,  are  the  origin  of  variations 
and  their  transmission  to  be  accounted  for  ? 

Every  individual  organism  reacts  more  or  less  markedly 
tinder  the  stress  of  environing  conditions.  The  reaction 
may  take  the  form  of  passive  resistance,  or  it  may  be 
exemplified  in  the  performance  of  specially  directed  motor- 
activities.  The  power  to  react  in  these  ways  is  inborn  ; 
but  the  degree  to  which  the  power  is  exercised  depends 
upon  the  conditions  of  existence,  and  during  the  life  of  the 
individual  the  power  may  be  increased  or  diminished  accord- 
ing to  whether  the  conditions  of  life  have  led  to  its  exercise 
or  not.  The  effects  of  training  and  exercise  on  the  per- 
formance of  muscular  feats  and  in  the  employment  of  mental 
faculties  are  too  well  known  to  need  special  exemplification. 
By  manual  labour  the  skin  of  the  hand  is  thickened ;  and 
by  long-continued  handling  of  a  rifle  a  bony  growth  caused 
by  the  weapon  in  drilling,  the  so-called  exercierknochen  of 
the  Germans,  is  developed.  Now,  it  is  clear  that  if  these 
acquired  structures  or  faculties  are  transmitted  from 
parent  to  offspring,  we  have  here  a  most  important  source 
and  origin  of  variations — a  source  from  which  spring  varia- 


Heredity  and  the  Origin  of  Variations.      147 

tions  just  in  the  particular  direction  in  which  they  are 
wanted.  The  question  is — Are  they  transmitted?  and  if 
so,  how  ? 

Let  us  begin  with  the  protozoa.  Dr.  Dallinger  made 
some  interesting  experiments  on  monads.  They  extended 
over  seven  years,  and  were  directed  towards  ascertaining 
whether  these  minute  organisms  could  be  gradually  ac- 
climatized to  a  temperature  higher  than  that  which  is 
normal  to  them.  Commencing  at  60°  Fahr.,  the  first 
four  months  were  occupied  in  raising  the  temperature 
10°  without  altering  the  life-history.  When  the  temperature 
of  73°  was  reached,  an  adverse  influence  appeared  to  be 
exerted  on  the  vitality  and  productiveness  of  the  organism. 
The  temperature  being  left  constant  for  two  months,  they 
regained  their  full  vigour,  and  by  gradual  stages  of  increase 
78°  was  reached  in  five  months  more.  Again,  a  long  pause 
was  necessary,  and  during  the  period  of  adaptation  a 
marked  development  of  vacuoles,  or  internal  watery  spaces, 
was  noticed,  on  the  disappearance  of  which  it  was  possible 
to  raise  the  temperature  higher.  Thus  by  a  series  of 
advances,  with  periods  of  rest  between,  a  temperature  of 
158°  Fahr.  was  reached.  It  was  estimated  that  the  re- 
search extended  over  half  a  million  generations.  Here, 
then,  these  monads  became  gradually  acclimatized  to  a 
temperature  more  than  double  that  to  which  their  ancestors 
had  been  accustomed  to — a  temperature  which  brought 
rapid  death  to  their  unmodified  relatives. 

Now,  in  such  observations  it  is  impossible  to  exclude 
elimination.  It  is  probable  that  there  were  numbers  of 
monads  which  were  unable  to  accommodate  themselves  to 
the  changed  conditions,  and  were  therefore  eliminated. 
But  in  any  case,  the  fact  remains  that  the  survivors  had, 
in  half  a  million  generations,  acquired  a  power  of  existing 
at  a  temperature  to  which  no  individual  in  its  single  life 
could  become  acclimatized.  Here,  then,  we  have  the 
hereditary  transmission  of  a  faculty.  But  the  organisms 
experimented  on  were  protozoa.  In  them  there  is  no  dis- 
tinction between  germ-cell  and  body-cell.  Multiplication 


148  Animal  Life  and  Intelligence. 

is  by  fission.  And  if  the  cell  which  undergoes  fission  has 
been  modified,  the  two  separate  cell-organisms  which  result 
from  that  fission  will  retain  the  special  modification.  In 
such  cases  the  transmission  of  acquired  characters  is  readily 
comprehensible.  We  have  an  hereditary  summation  of 
effects. 

With  the  metazoa  the  case  is  different.  In  the  higher 
forms  the  germinal  cells  are  internal  and  sheltered  from 
environing  influences  by  the  protecting  body-wall.  It  is 
the  body-cells  that  react  to  environmental  stresses;  it  is 
muscle  and  nerve  in  which  faculty  is  strengthened  by  use 
and  exercise,  or  allowed  to  dwindle  through  neglect.  The 
germ-cells  are  shielded  from  external  influences.  They 
lead  a  sheltered  and  protected  life  within  the  body-cavity. 
It  is  no  part  of  their  business  to  take  part  in  either  passive 
resistance  or  responsive  activity.  During  the  individual 
life,  then,  the  body  may  be  modified,  may  acquire  new 
tissue,  may  by  exercise  develop  enhanced  faculties.  But 
can  the  body  so  modified  affect  the  germ-cells  which  it 
carries  within  it  ? 

Biologists  are  divided  on  this  question.  Some  say  that 
the  body  cannot  affect  the  germ  ;  others  believe  that  it  can 
and  does  do  so. 

It  might  seem  an  easy  matter  to  settle  one  way  or 
another.  But,  in  truth,  it  is  by  no  means  so  easy.  Suppose 
that  a  man  by  strenuous  exercise  brings  certain  muscles  to 
a  high  degree  of  strength  or  co-ordination.  His  son  takes 
early  to  athletics,  and  perhaps  excels  his  parent.  Is  this 
a  case  of  transmitted  fibre  and  faculty  ?  It  may  be.  But 
how  came  it  that  the  father  took  to  athletics,  and  was 
enabled  to  develop  so  lithe  and  powerful  a  frame  ?  It  must 
have  been  "  in  him,"  as  we  say.  In  other  words,  it  must 
have  been  a  product  of  the  germ-cells  from  which  he  was 
developed.  And  since  his  son  was  developed,  in  part  at 
least,  from  a  germ- cell  continuous  with  these,  what  more 
natural  than  that  he  too  should  have  an  inherent  athletic 
habit  ?  Every  faculty  that  is  developed  in  any  individual 
is  potential  in  the  germ-stuff  from  which  he  springs ;  the 


Heredity  and  the  Origin  of  Variations.      149 

tendency  to  develop  any  particular  faculty  is  there  too  ; 
and  both  faculty  and  tendency  to  exercise  it  are  handed 
on  by  the  continuity  of  germ-protoplasm  or  germ-cells. 
Logically,  there  is  no  escape  from  the  argument  if  put  as 
follows:  The  body  and  all  its  faculties  (I  use  the  term 
"faculties  "  in  the  broadest  possible  sense)  are  the  product 
of  the  germ;  the  acquisition  of  new  characters  or  the 
strengthening  of  old  faculties  by  the  body  is  therefore  a 
germinal  product ;  there  is  continuity  of  the  germs  of 
parent  and  child;  hence  the  acquisition  by  the  child  of 
characters  acquired  by  the  parent  is  the  result  of  germinal 
or  cellular  continuity.  It  is  not  the  acquired  character 
which  influences  the  germ,  but  the  germ  which  develops 
what  appears  to  be  an  acquired  character.  Finally,  if  an 
acquired  character,  so  called,  is  better  developed  in  the 
child  than  in  the  parent,  what  is  this  but  an  example  of 
variation  ?  And  if,  in  a  series  of  generations,  the  acquired 
character  continuously  increases  in  strength,  this  must 
be  due  to  the  continued  selection  of  favourable  variations. 
It  is  clear  that  the  organism  that  best  uses  its  organs 
has,  other  things  equal,  the  best  chance  of  survival.  It 
will  therefore  hand  on  to  its  offspring  germinal  matter 
with  an  inherent  tendency  to  make  vigorous  use  of  its 
faculties. 

Those  who  argue  thus  deny  that  the  body-cells  can  in 
any  way  affect  the  germ-cells.  To  account  for  any  con- 
tinuous increase  in  faculty,  they  invoke  variation  and  the 
selection  of  favourable  varieties.  What,  then,  we  may  now 
ask,  is,  on  their  view,  the  mode  of  origin  of  variations  ? 

In  sexual  reproduction,  with  the  union  of  ovum  and 
sperm,  we  seem  to  have  a  fertile  source  of  variation.  The 
parents  are  not  precisely  alike,  and  their  individual 
differences  are,  ex  hypothesi,  germinal  products.  In  the 
union  of  ovum  and  sperm,  therefore,  we  see  the  union  of 
somewhat  dissimilar  germs.  And  in  sexual  reproduction 
we  have  a  constantly  varying  series  of  experiments  in 
germinal  combinations,  some  of  which,  we  may  fairly  sup- 
pose, will  be  successful  in  giving  rise  to  new  or  favourable 


150  Animal  Life  and  Intelligence. 

variations.  This  view,  however,  would  seem  to  involve  an 
hypothesis  which  may  be  true,  but  which,  in  any  case, 
should  be  indicated.  For  it  is  clear  that  if  new  or  favour- 
able variations  arise  in  this  way,  the  germinal  union 
cannot  be  a  mere  mixture,  but  an  organic  combination. 

An  analogy  will  serve  to  indicate  the  distinction  implied 
in  these  phrases.  It  is  well  known  that  if  oxygen  and 
hydrogen  be  mixed  together,  at  a  temperature  over  100°  C., 
there  will  result  a  gaseous  substance  with  characters  inter- 
mediate between  those  of  the  two  several  gases  which  are 
thus  commingled.  But  if  they  are  made  to  combine,  there 
will  result  a  gas,  water-vapour,  with  quite  new  properties 
and  characters.  In  like  manner,  if,  in  sexual  union,  there 
is  a  mere  mixture,  a  mere  commingling  of  hereditary 
characters,  it  is  quite  impossible  that  new  characters 
should  result,  or  any  intensification  of  existing  characters 
be  produced  beyond  the  mean  of  those  of  ovum  and  sperm. 
If,  for  example,  it  be  true,  as  breeders  believe,  that  when 
an  organ  is  strongly  developed  in  both  parents  it  is  likely 
to  be  even  more  strongly  developed  in  the  offspring,  and 
that  weakly  parts  tend  to  become  still  weaker,  this  cannot 
be  the  result  of  germinal  mixture.  Let  us  suppose,  for 
the  sake  of  illustration,  that  a  pair  of  organisms  have  each 
an  available  store  of  forty  units  of  growth-force,  and  that 
these  are  distributed  among  five  sets  of  organs,  a  to  e,  as 
in  the  first  two  columns.  Then  the  offspring  will  show  the 
organs  as  arranged  in  the  third  column.* 


40  40  40 


*  Latency  is  here  neglected.  Mr.  Francis  Galton  lias  shown,  statistically, 
that  the  offspring,  among  human  folk,  inherit  J  from  each  parent,  T'g  from 
each  grandparent,  and  the  remaining  J  from  more  remote  ancestors.  In 
d  >mesticated  animals,  reversion  to  characters  of  distant  ancestors  sometimes 
occurs.  This,  however,  does  not  invalidate  the  argument  in  the  text,  which 


Heredity  and  the  Origin  of  Variations.      151 

There  is  no  increase  in  the  set  of  organs  a,  which  are 
strongly  developed  in  both  parents  ;  and  no  decrease  in 
the  set  of  organs  e,  which  are  weakly  developed  in  both 
parents.  By  sexual  admixture  alone  there  can  be  no 
increase  or  decrease  beyond  the  mean  of  the  two  parental 
forms.  If,  then,  the  union  of  sperm  and  ovum  be  the 
source  of  new  or  more  favourable  variations  other  than  or 
stronger  than  those  of  either  parent,  this  must  be  due  to 
the  fact  that  the  hereditary  tendencies  not  merely  com- 
mingle, but  under  favourable  conditions  combine,  in  some 
way  different  indeed  from,  but  perhaps  analogous  to,  that  / 
exemplified  in  chemical  combination. 

Such  organic  combination,  as  opposed  to  mere  com- 
mixture, is  altogether  hypothetical,  but  it  may  be  worth 
while  to  glance  at  some  of  its  implications.  If  it  be 
analogous  to  chemical  combination,  the  products  would 
be  of  a  definite  nature;  in  other  words,  the  variations 
would  be  in  definite  directions.  Selection  and  elimination 
would  not  have  to  deal  with  variations  in  any  and  all 
directions,  but  would  have  presented  to  them  variations 
specially  directed  along  certain  lines  determined  by  the 
laws  of  organic  combination.  As  Professor  Huxley  has' 
said,  "  It  is  quite  conceivable  that  every  species  tends  to 
produce  varieties  of  a  limited  number  and  kind,  and  that 
the  effect  of  natural  selection  is  to  favour  the  development 
of  some  of  these,  while  it  opposes  the  development  of  others 
along  their  predetermined  line  of  modification."  Mr. 
Gulick  *  and  others  have  been  led  to  believe  in  a  tendency 
to  divergent  evolution  residing  in  organic  life-forms.  Such 
a  tendency  might  be  due  to  special  modes  of  organic  com- 
bination giving  rise  to  particular  lines  of  divergence. 
Again,  we  have  seen  that  some  naturalists  believe  that 
specific  characters  are  not  always  of  utilitarian  significance. 
But,  as  was  before  pointed  out,  on  the  hypothesis  of  all- 
is  that  sexual  admixture  tends  towards  the  mean  of  the  race  (ancestors 
included),  and  cannot  be  credited  with  new  and  unusually  favourable  variations. 
The  prepotency  of  one  parent  is  also  here  neglected. 

*  See  his  valuable  paper  on  "  Divergent  Evolution,"  Lin.  Soc.  Zool.,  No.  cxx. 


152  Animal  Life  and  Intelligence. 

round  variation,  there  is  nothing  to  give  these  non-useful 
specific  characters  fixity  and  stability,  nothing  to  prevent 
their  being  swamped  by  intercrossing.  If,  however,  on  the 
hypothesis  of  combination,  we  have  definite  organic  com- 
pounds, instead  of,  or  as  well  as,  mere  hereditary  mixtures ; 
if,  in  other  words,  variations  take  definite  lines  determined 
by  the  laws  of  organic  combination  (as  the  nature  and 
properties  of  chemical  compounds  are  determined  by  the 
laws  of  chemical  combination) ,  then  this  difficulty  disappears. 
There  is  no  reason  why  a  neutral  divergence — one  neither 
useful  nor  deleterious — should  be  selected  or  eliminated. 
And  if  its  direction  is  predetermined,  there  is  no  reason 
why  it  should  not  persist,  though,  of  course,  it  will  not  be 
kept  at  a  high  standard  by  elimination.  It  has  again  and 
again  been  pointed  out  as  a  difficulty  in  the  path  of  natural 
selection  that,  in  their  first  inception,  certain  characters  or 
structures  cannot  yet  be  of  sufficient  utility  to  give  the 
possessor  much  advantage  in  the  struggle  for  existence. 
If,  however,  these  be  definite  products  of  organic  combina- 
tion, this  difficulty  also  disappears.  So  long  as  they  are 
not  harmful,  they  will  not  be  eliminated,  and  by  fortunate 
combinations  will  progress  slowly  until  natural  selection 
gets  a  hold  on  them  and  pushes  them  forward,  developing 
to  the  full  the  inherent  tendency.  Finally,  we  must  notice 
that,  on  this  hypothesis,  our  conception  of  panmixia,  or 
intercrossing,  would  have  to  be  modified.  As  generally 
held,  this  doctrine  is  based  upon  hereditary  mixture,  not 
organic  combination.  It  is  a  doctrine  of  means  and 
averages.  There  is  a  good  deal  of  evidence  that  inter- 
crossing does  not,  at  least  in  all  cases,  produce  mean  or 
average  results.  And  according  to  the  hypothesis  of 
organic  combination,  it  need  not  always  do  so.  According 
to  this  hypothesis,  then,  divergent  modifications  might  arise 
and  be  perpetuated  without  the  necessity  of  isolation. 
Sterility  might  result  from  the  fact  that  divergence  had 
been  carried  so  far  that  organic  combination  was  no  longer 
possible ;  reversion,  due  to  intercrossing,  from  the  fact 
that  combinations  long  rendered  impossible  by  the  isolation 


Heredity  and  the  Origin  of  Variations.     153 

of  the  necessary  factors  in  distinct  varieties,  are  again 
rendered  possible  when  these  varieties  interbreed. 

On  this  hypothesis  of  organic  combination,  to  which  we 
shall  recur  in  the  chapter  on  "  Organic  Evolution,"  the 
varied  forms  of  animal  life  are  the  outcome  of  definite 
organic  products  with  definite  organic  structure,  analogous 
to  the  definite  chemical  compounds  with  definite  crystalline 
and  molecular  structure ;  and  the  analogy  between  the 
regeneration  of  hydra  and  the  reconstruction  of  a  crystal 
is  carried  on  a  step  further.  I  do  not  say  that  I  am  myself 
at  present  prepared  to  adopt  the  hypothesis,  at  least  in 
this  crude  form ;  but  it  is,  perhaps,  worth  a  passing  con- 
sideration. Its  connection  with  Mr.  Herbert  Spencer's 
doctrine  of  physiological  units  is  obvious.  The  analogy 
there  is  with  crystallization ;  here  it  is  with  chemical 
combination. 

We  must  now  return  to  the  point  which  gave  rise  to 
this  digression,  and  repeat  that  mere  hereditary  com- 
mixture in  the  union  of  ovum  and  sperm  cannot  give  rise 
to  new  characters  or  raise  existing  structures  (1)  where 
there  is  free  intercrossing  beyond  the  mean  of  the  species, 
and  (2)  where  there  is  rigorous  elimination  beyond  the 
existing  maximum  of  the  species.  Variations  beyond  this 
existing  maximum  must  be  due  to  some  other  cause. 

Professor  Weismann  has  suggested,  as  a  cause  of  varia- 
tion, the  extrusion  of  the  polar  cells  from  the  ovum.  It 
has  before  been  mentioned  that,  generally  previous  to 
fertilization,  the  ripe  ovum  buds  off  two  minute  polar 
bodies.  The  nucleus  of  the  ovum  divides,  and  one  half  is 
extruded  in  the  first  polar  cell ;  the  nucleus  then  (except  in 
parthenogenetic  *  forms,  where  there  is  no  union  of  ovum 
and  sperm)  again  divides,  and  a  second  polar  cell  is  extruded. 
In  accordance  with  his  special  view  of  the  absolute  dis- 
tinction between  the  body-plasm  and  the  germ-plasm,  the 
first  polar  cell  is  formed  to  carry  off  the  body-plasm  of  the 

*  One  parthenogenetic  form — the  drone — has  been  shown  by  Blochmann 
to  extrude  a  second  polar  cell.  This  observation  is  in  serious  opposition  to 
Dr.  Weismann's  theory. 


154  Animal  Life  and  Intelligence. 

ovum-nucleus.  For  the  ovum,  besides  being  a  germ-bearer, 
is  a  specialized  cell,  and  its  special  form  is  determined  by 
the  body-plasm  it  contains.  This  is  got  rid  of  in  the  first 
polar  cell,  and  nothing  but  germ-plasm  remains.  Now, 
if  nothing  further  took  place,  all  the  ova  of  this  same 
individual  containing  similar  germ-plasm  would  be  identical, 
and  similarly  with  all  the  sperms  from  the  same  parent. 
The  union  of  these  similar  ova  from  one  parent  with  similar 
sperms  from  another  should  therefore  give  rise  to  similar 
offspring.  But  the  offspring  are  not  all  similar;  they 
vary.  Professor  Weisrnann  here  makes  use  of  the  second 
polar  cell.*  "  A  reduction  of  the  germ-plasm,"  he  says, 
"  is  brought  about  by  its  formation,  a  reduction  not  only 
in  quantity,  but  above  all,  in  the  complexity  of  its  constitu- 
tion. By  means  of  the  second  nuclear  division,  the  excessive 
accumulation  of  different  kinds  of  hereditary  tendencies  or 
germ-plasms  is  prevented.  With  the  nucleus  of  the  second 
polar  body,  as  many  different  kinds  of  plasm  are  removed 
from  the  egg  as  will  be  afterwards  introduced  by  the  sperm- 
nucleus."  "  If,  therefore,  every  egg  expels  half  the  number 
of  its  ancestral  germ-plasms  during  maturation,  the  germ- 
cells  of  the  same  mother  cannot  contain  the  same  hereditary 
tendencies,  unless  we  make  the  supposition  that  corre- 
sponding ancestral  germ-plasms  chance  to  be  retained  by 
all  eggs— a  supposition  that  cannot  be  sustained." 

The  two  polar  cells  are  therefore,  on  this  view,  of  totally 
different  character ;  and  the  nuclear  division  in  each  case 
of  a  special  kind  and  sui  generis.  I  do  not  think  that  the 
evidence  afforded  by  observation  lends  much  support  to 
this  view.  But  with  that  we  are  not  here  specially  con- 
cerned. We  have  to  consider  how  this  reduction  of  the 
number  of  ancestral  germ-plasms  can  further  the  kind  of 
variation  required.  Now,  it  is  difficult  to  see,  and  Professor 
Weismann  does  not  explain,  how  the  getting  rid  of  certain 
ancestral  tendencies  can  give  rise  to  new  characters  or  the 
enhancement  of  old  characters.  One  can  understand  how 
this  "reducing  division,"  as  Dr.  Weismann  calls  it,  can 

*  Weismann,  "Essays  on  Heredity,"  pp.  355,  b78. 


Heredity  and  the  Origin  of  Variations.     155 

reduce  the  level  of  now  one  and  now  another  character. 
But  how  it  can  raise  the  level  beyond  that  attained  by 
either  parent  is  not  obvious.  It  is  perhaps  possible,  though 
Professor  Weismann  does  not,  I  think,  suggest  it,  that,  by 
a  kind  of  compensation,*  the  reduction  of  certain  characters 
may  lead  to  the  enhancement  of  others.  Let  us  revert  to 
the  illustration  on  p.  150,  where  each  individual  has  an 
available  store  -of  forty  units  of  growth- force ;  and  let  us 
express  by  the  minus  sign  the  units  lost  in  the  parents  by 
the  extrusion  of  the  polar  cell  and  an  analogous  process 
which  may  occur  in  the  genesis  of  the  sperm.  Then  the 
units  of  growth-force  which  may  thus  be  lost  by  a  "  reducing 
division  "  in  b,  c,  and  e  may  be,  in  the  offspring,  applied 
to  the  further  growth  of  a ;  thus — 


a     10  10         14 

b     8-1  10-3      7 

c    9-1  5-1      6 

d     7  9        8 

e     6-2  6         5 

Here  the  reduction  of  the  characters  b,  c,  and  e  has 
led  to  the  enhancement  of  a,  which  thus  stands  at  a  higher 
level  than  in  either  parent. 

On  such  an  hypothesis  we  may,  perhaps,  explain  the 
fact  to  which  breeders  of  stock  testify — that  the  organ 
strongly  developed  in  both  parents  (a)  is  yet  more  strongly 
developed  in  some  of  their  offspring,  and  that  weakly  parts 
(e)  tend  to  become  still  weaker.  I  know  not  whether  this 
way  of  putting  the  matter  would  commend  itself  to  Professor 
Weismann  or  his  followers ;  but  some  such  additional 
hypothesis  of  transference  of  growth-force  from  one  set  of 
organs  to  another  set  of  organs  seems  necessary  to  complete 
his  hypothesis. 

Professor  Weismann's  view,  then,  assumes  (1)  that  the 
cell-division  which  gives  rise  to  the  ova  in  the  ovary  is  so 
absolutely  equal  and  similar  that  all  ova  have  precisely 

*  The  law  of  compensation  of  growth  or  balancemeut  was  suggested  at 
nearly  the  same  time  by  Goethe  and  Geoffroy  Saint-Hilaire.  The  application 
iii  the  text  lias  not,  so  far  as  I  know,  been  before  suggested. 


156  Animal  Life  and  Intelligence. 

the  same  characters ;  (2)  that  the  first  polar  cell  leaves 
the  germinal  matter  unaffected,  merely  getting  rid  of 
formative  body-plasm ;  (3)  that  the  nuclear  division  giving 
rise  to  the  second  polar  cell  is  unequal  and  dissimilar, 
effecting  the  differential  reduction  of  ancestral  germ- 
plasms.  Concerning  all  of  which  one  can  only  say  that 
it  may  be  so,  but  that  there  is  not  much  evidence  that  it 
is  so.  And,  without  strong  confirmatory  evidence,  it  is 
questionable  whether  we  are  justified  in  assuming  these 
three  quite  different  modes  of  nuclear  division. 

There  remains  one  more  question  for  consideration,  on 
the  hypothesis  that  the  germ-cells  cannot  in  any  special 
way  be  affected  by  the  body-cells.  In  considering  the 
union  of  ovum  and  sperm  as  a  source  of  variation,  we  have 
taken  for  granted  the  existence, of  variations.  We  have 
been  dealing  with  the  mixture  or  combination  of  already 
existing  variations.  How  were  variations  started  in  the 
first  instance  ? 

We  have  already  seen  that  in  the  protozoa  parent  and 
offspring  are  still,  in  a  certain  sense,  one  and  the  same 
thing ;  the  child  is  a  part,  and  usually  half,  of  the  parent. 
If,  therefore,  the  individuals  of  a  unicellular  species  are 
acted  upon  by  any  of  the  various  external  influences,  it  is 
inevitable  that  hereditary  individual  differences  will  arise 
in  them ;  and,  as  a  matter  of  fact,  it  is  indisputable  that 
changes  are  thus  produced  in  these  organisms,  and  that 
the  resulting  characters  are  transmitted.  Hereditary 
variability  cannot,  however,  arise  in  the  metazoa,  in  which 
the  germ-plasm  and  the  body-plasm  are  differentiated  and 
kept  distinct.  It  can  only  arise  in  the  lowest  unicellular 
organisms.  But  when  once  individual  difference  had  been 
attained  by  these,  it  necessarily  passed  over  into  the 
higher  organisms  when  they  first  appeared.  Sexual  repro- 
duction coming  into  existence  at  the  same  time,  the 
hereditary  differences  were  increased  and  multiplied,  and 
arranged  in  ever-changing  combinations.  Such  is  Pro- 
fessor Weismann's  solution  of  the  difficulty,  told,  for  the 
most  part,  in  his  own  words, 


Heredity  and  the  Origin  of  Variations.      157 

I  do  not  know  that  Professor  Weismann  has  anywhere 
distinctly  stated  what  he  conceives  to  be  the  relation  of 
body-plasm  and  germ-plasm  in  the  protozoa.  Are  the  two 
as  yet  undifferentiated  ?  This  can  hardly  be  so,  seeing  the 
fundamental  distinction  he  draws  between  them.  Is  it 
the  germ-plasm  or  the  body-plasm  that  is  influenced  by 
external  stresses?  If  the  former,  does  it  transfer  its 
influence  to  the  body-plasm  during  the  life  of  the  indi- 
vidual? If  the  latter,  then  the  body-plasm  must  either 
directly  influence  the  germ-plasm  in  unicellular  organisms 
(it  would  seem  that,  according  to  Professor  Weismann,  it 
cannot  do  so  in  the  metazoa),  or  the  changed  body-plasm, 
which  shares  in  the  fission  of  the  protozoon,  must  participate 
in  that  so-called  immortality  which  is  often  said  to  be  the 
special  prerogative  of  germinal  matter. 

These,  however,  are  matters  for  Professor  Weismann 
and  his  followers  to  settle.  I  regard  the  sharp  distinction 
between  body-plasm  and  germ-plasm  as  an  interesting 
biological  myth.  For  me,  it  is  sufficient  that  the  proto- 
plasm of  the  protozoon  is  modified,  and  the  modification 
handed  on  in  fission.  And  it  is  clear  that  Professor 
Weismann  is  correct  in  saying  that  the  commixture  or 
combination  of  characters  takes  its  origin  among  the 
protozoa.  If  the  unicellular  individuals  are  differently 
modified,  however  slightly,  then,  whenever  conjugation 
occurs  between  two  such  individuals,  there  will  be  a  com- 
mingling or  combination  of  the  different  characters.  The 
transmissible  influence  of  the  environment,  however,  ceases 
when  the  metazoon  status  is  reached,  and  special  cells  are 
set  apart  for  reproductive  purposes — ceases,  that  is  to  say, 
in  so  far  as  the  influence  on  the  body  is  concerned.  There 
may,  of  course,  be  still  some  direct*  influence  on  the 
germinal  cells  themselves.  Except  for  this  further  in- 
fluence, the  metazoon  starts  with  the  stock  of  variations 

*  Darwin  spoke  of  changed  conditions  acting  "  directly  on  the  organization 
or  indirectly  through  the  reproductive  system."  Now,  since  Professor  Weis- 
mann has  taught  us  to  reconsider  these  questions,  we  speak  of  such  conditions 
as  acting  directly  on  the  germ  or  indirectly  through  the  body.  The  germ  is 
no  longer  subordinate  to  the  body,  but  the  body  to  the  germ. 


158  Animal  Life  and  Intelligence. 

acquired  by  that  particular  group  of  protozoa — whatever  it 
may  be — from  which  it  originated.  All  future  variations 
in  even  the  highest  metazoa  arise  from  these. 

Now,  it  is  obvious  that  no  mere  commingling  and  re- 
arrangement of  protozoan  characters  could  conceivably 
give  rise  to  the  indefinitely  more  complex  metazoan 
characters.  But  if  there  be  a  combination  and  recom- 
bination of  these  elements  in  ever-varying  groups,  the 
possibilities  are  no  longer  limited.  Let  us  suppose  that 
three  simple  protozoan  characters  were  acquired.  The 
mere  commixture  of  these  three  could  not  give  much  scope 
for  further  variation.  It  would  be  like  mixing  carbon, 
oxygen,  and  hydrogen  in  varying  proportions.  But  let 
them  in  some  way  combine,  and  you  have,  perhaps,  such 
varied  possibilities  as  are  open  to  chemical  combinations 
of  oxygen,  hydrogen,  and  carbon,  whose  name  is  legion, 
but  whose  character  is  determined  by  the  laws  of  chemical 
combination. 

Summing  up  now  the  origin  of  variations,  apart  from 
those  which  are  merely  individual,  on  the  hypothesis  that 
particular  modifications  of  the  body-cells  cannot  be  trans- 
mitted to  the  germ-cells,  we  have — 

1.  In  protozoa,  the  direct  influence  of  the  environment 
and  the  induced  development  of  faculty. 

2.  In  metazoa — 

(a)  Some  direct  and  merely  general  influence   of  the 
environment  on  the  germ,  including  under  the  term  "  en- 
vironment "  the  nutrition,  etc.,  furnished  by  the  body. 

(b)  The  combination  and  recombination  of  elementary 
protoplasmic  faculties  (specific  molecular  groupings)   ac- 
quired by  the  protozoa. 

(c)  Influences  on  the  germ,  the  nature  of  which  is  at 
present  unknown. 

We  may  now  pass  on  to  consider  the  position  of  those 
who  give  an  affirmative  answer  to  the  question — Can  the 
body  affect  the  germ  ?  Two  things  are  here  required. 
First,  definite  evidence  of  the  fact  that  the  body  does  so 


Heredity  and  the  Origin  of  Variations.      159 

affect  the  germ ;  i.e.  that  acquired  characters  are  inherited. 
Secondly,  some  answer  to  the  question — How  are  the  body- 
cells  able  to  transmit  their  modifications  to  the  germ-cells  ? 
We  will  take  the  latter  first,  assuming  the  former  point  to 
be  admitted. 

Let  us  clearly  understand  the  question.  An  individual, 
in  the  course  of  its  life,  has  some  part  of  the  epidermis,  or 
skin,  thickened  by  mechanical  stresses,  or  some  group  of 
muscles  strengthened  by  use,  or  the  activity  of  certain 
brain-cells  quickened  by  exercise :  how  are  the  special 
modifications  of  these  cells,  here,  there,  or  elsewhere  in  the, 
body,  communicated  to  the  germ,  so  that  its  products  are 
similarly  modified  in  the  offspring  ?  The  following  are 
some  of  the  hypotheses  which  have  been  suggested : — 

(a)  Darwin's  pangenesis. 

(6)  Haeckel's  perigenesis ;  Spencer's  physiological  units. 

(c)  The  conversion  of  germ-plasm  into  body-plasm,  and 
its  return  to  the  condition  of  germ-plasm  (Nageli). 

(d)  The  unity  of  the  organism. 

(a)  Concerning  pangenesis,  nothing  need  be  added  to 
what  has  already  been  said.     Although,  as  we  have  seen, 
it  has  been  adopted  with  modifications  by  Professor  Brooks  ; 
although  Mr.  Francis  Galton,  a  thinker  of  rare  ability  and 
a  pioneer  in  these  matters,  while  contending  for  continuity, 
admitted  a  little  dose  of  pangenesis ;    although  De  Vries 
has  recently  renewed  the  attempt  to  combine  continuity 
and  a  modified  pangenesis ; — this  hypothesis  does  not  now 
meet  with  any  wide  acceptance. 

(b)  With  the  pamphlet    in  which   Professor  Haeckel 
brought  forward  his  hypothesis  termed  the  perigenesis  of 
the  plastidule,   I  cannot   claim  first-hand  acquaintance. 
According   to   Professor  Bay  Lankester,  who   gave  some 
account  of  it  in  Nature,*  protoplasm  is  regarded  by  Haeckel 
as  consisting  of  certain  organic  molecules  called  plasti- 
dules.    These  plastidules  are  possessed  of  special  undulatory 
movements,  or  vibrations.     They  are  liable  to  have  their 
undulations   affected  by   every   external  force,  and,  once 

*  July  15,  1876.   Since  reprinted  iu  "  The  Advancement  of  Science,"  p.  273. 


160  Animal  Life  and  Intelligence. 

modified,  the  movement  does  not  return  to  its  pristine 
condition.  By  assimilation,  they  continually  increase  to  a 
certain  size  and  then  divide,  and  thus  perpetuate  in  the 
undulatory  movement  of  successive  generations  the  im- 
pressions or  resultants  due  to  the  action  of  external 
agencies  on  the  individual  plastidules.  On  this  view,  then, 
the  form  and  structure  of  the  organism  are  due  to  the 
special  mode  of  vibration  of  the  constituent  plastidules. 
This  vibration  is  affected  by  external  forces.  The  modified 
vibration  is  transmitted  to  the  plastidules  by  the  germ, 
which,  therefore,  produce  a  similarly  modified  organism. 
As  Mr.  J.  A.  Thomson  says,  "In  metaphorical  language, 
the  molecules  remember  or  persist  in  the  rhythmic  dance 
which  they  have  learned." 

Darwin's  hypothesis  was  frankly  and  simply  organic — 
the  gemmules  are  little  germs.  This  of  Professor  Haeckel 
tries  to  go  deeper,  and  to  explain  organic  phenomena  in 
terms  of  molecular  motion.  Mr.  Herbert  Spencer  long  ago 
suggested  that,  just  as  molecules  are  built  up,  through 
polarity,  into  crystals,  so  physiological  units  are  built  up, 
under  the  laws  of  organic  growth,  into  definite  and  special 
organic  forms.  Both  views  involve  special  units.  With 
Mr.  Herbert  Spencer,  their  "  polarity  "  is  the  main  feature ; 
with  Professor  Haeckel,  their  "undulatory  movements." 
According  to  Mr.  Spencer,  "  if  the  structure  of  an  organism 
is  modified  by  modified  function,  it  will  impress  some 
corresponding  modification  on  the  structures  and  polarities 
of  its  units."  *  According  to  Professor  Haeckel,  the  vibra- 
tions of  the  plastidules  are  permanently  affected  by  external 
forces.  In  either  case,  an  explanation  is  sought  in  terms 
of  molecular  science,  or  rather,  perhaps,  on  molecular 
analogies.  So  far  good.  Such  "  explanation,"  if  hypo- 
thetical, may  be  suggestive.  It  may  well  be  that  the  pos- 
sibilities of  fruitful  advance  will  be  found  on  these  lines. 

But  though,  as  general  theories,  these  suggestions  may 
be  valuable,  they  do  not  help  us  much  in  the  comprehen- 
sion of  our  special  point.  To  talk  vaguely  about  "  undula- 

*  Herbert  Spercer,  "  Principles  of  Biology,"  vol.  i.  p.  256. 


Heredity  and  the  Origin  of  Variations.     161 

torj  movements  "  or  "  polarities  "  does  not  enable  us  to 
comprehend  with  any  definiteness  how  this  particular  modi- 
fication of  these  particular  nerve-cells  is  so  conveyed  to  the 
germ  that  it  shall  produce  an  organism  with  analogous 
nerve-cells  modified  in  this  particular  way. 

(c)  The  hypothesis  that  the  germ-plasm  may  be  con- 
verted into  body-plasm,  which,  on  its  return  again  to  the 
condition  of  germ-plasm,  may  retain  some  of  the  modifi- 
cations it  received  as  body-plasm,  seems  to  be  negatived, 
so  far  as  most  animals   are   concerned,  by  the  facts  of 
embryology  and  development.     The  distinction  of  germ- 
plasm  and  body-plasm  I  hold  to  be  mythical.     And  there 
is   no  evidence  that  cells    specially  differentiated   along 
certain  lines  can  become  undifferentiated  again,  and  then 
contribute  to  the  formation  of  ova  or  sperms.     From  the 
view-point  of  cell- differentiation,  which  seems  to  me  the 
most  tenable  position,  there  does  not  seem  any  evidence 
for,  or  any  probability  of,  the  occurrence  of  any  roundabout 
mode  of  development  of  the  germinal  cells  which  could 
enable  them  to  pick  up  acquired  characters  en  route. 

(d)  We  come  now  to  the  contention  that  the  organism, 
being  one  and  continuous,  if  any  member  suffers,  the  germ 
suffers  with  it.     The  organs  of  the  body  are  not  isolated  or 
insulated ;  the  blood  is  a  common  medium ;   the  nerves 
ramify  everywhere  ;  the  various   parts   are  mutually  de- 
pendent :  may  we  not,  therefore,  legitimately  suppose  that 
long-continued  modification  of  structure  or  faculty  would 
soak  through  the  organism  so  completely  as  eventually  to 
modify  the  germ  ?    The  possibility  may  fairly  be  admitted. 
But  how  is  the  influence  of  the  body  brought  to  bear  on 
the   germ  ?     The   common  medium  of  the  blood,  proto- 
plasmic continuity,  the  influence  of  the  products  of  chemical 
or  organic  change, — these  are  well  enough  as  vague  sug- 
gestions.    But  how  do  they  produce  their  effects  ?    Once 
more,  how  is  this  increased  power  in  that  biceps  muscle 
of  the  oarsman  able  to  impress  itself  upon  the  sperms  or 
the  ova  ?     No_defini^e  answer  can  be  given. 

We  are  obliged  to  confess,  then,  that  no  definite  and 

M 


1 62  Animal  Life  and  Intelligence. 

satisfactory  answer  can  be  given  to  the  question — How  can 
the  body  affect  the  germ  so  that  this  or  that  particular 
modification  of  body-cells  may  be  transmitted  to  the 
offspring  ?  We  may  make  plausible  guesses,  or  we  may 
say — I  know  not  how  the  transmission  is  effected ;  but  there 
is  the  indubitable  fact. 

This  leads  us  to  the  evidence  of  the  fact. 

It  must  be  remembered  that  no  one  questions  the 
modifiability  of  the  individual.  That  the  epidermis  of  the 
oarsman's  hand  is  thickened  and  hardened  ;  that  muscles 
increase  by  exercise;  that  the  capacity  for  thinking  may 
be  developed  by  steady  application  ; — these  facts  nobody 
doubts.  That  well-fed  fish  grow  to  a  larger  size  than  their 
ill-fed  brethren;  that  if  the  larger  shin-bone  (the  tibia) 
of  a  dog  be  removed,  the  smaller  shin-bone  (the  fibula)  soon 
acquires  a  size  equal  to  or  greater  than  that  of  the  normal 
tibia  ;  that  if  the  humerus,  or  arm-bone,  be  shifted  through 
accident,  a  new  or  false  joint  will  be  formed,  while  the  old 
cavity  in  which  the  head  of  the  bone  normally  works,  fills 
up  and  disappears  ;  that  canaries  fed  on  cayenne  pepper 
have  the  colour  of  the  plumage  deepened,  and  bullfinches 
fed  on  hemp-seed  become  black ;  that  the  common  green 
Amazonian  parrot,  if  fed  with  the  fat  of  siluroid  fishes, 
becomes  beautifully  variegated  with  red  and  yellow  ;  that 
climate  affects  the  hairiness  of  mammals ; — these  and  many 
other  reactions  of  the  individual  organism  in  response  to 
environing  conditions,  will  be  admitted  by  every  one.* 
That  constitutional  characters  of  germinal  origin  are  in- 
herited is  also  universally  admitted.  The  difficulty  is  to 
produce  convincing  evidence  that  what  is  acquired  is  really 
inherited,  and  what  is  inherited  has  been  really  acquired. 

Attempts  have  been  made  to  furnish  such  evidence  by 
showing  that  certain  mutilations  have  been  inherited.  I 
question  -whether  many  of  these  cases  will  withstand  rigid 

*  Mr.  J.  A.  Thomson  has  published  a  most  valuable  "  Synthetic  Summary 
of  the  Influence  of  the  Environment  upon  the  Organism  "  (Proceedings  Koyal 
Physiological  Society,  Edinburgh  :  vol.  ix.  pt.  o,  1888).  The  case  of  the 
Amaz"niau  parrots  was  communicated  to  Darwin  by  Mr. Wallace  ("Animals 
and  Plants  under  Domestication,"  vol.  ii.  p.  269). 


Heredity  and  the  Origin  of  Variations.      163 

criticism.  Nor  do  I  think  that  mutilations  are  likely  to 
afford  the  right  sort  of  evidence  one  way  or  the  other.  We 
must  look  to  less  abnormal  influences.  What  we  require 
is  evidence  in  favour  of  or  against  the  supposition  that 
modifications  of  the  body-cells  are  transmitted  to  the  germ- 
cells.  Now,  these  modifications  must  clearly  be  of  such  a 
nature  as  to  be  receivable  by  the  cells  without  in  any  way 
destroying  their  integrity.  The  destruction  or  removal  of 
cells  is  something  very  different  from  this.  If  it  were 
proved  that  mutilations  are  inherited,  this  would  not 
necessarily  show  that  normal  cell-modifications  are  trans- 
missible. And  if  the  evidence  in  favour  of  inherited 
mutilations  breaks  down,  as  I  believe  it  does,  this  does  not 
show  that  more  normal  modifications  such  as  those  with 
which  we  are  familiar,  as  occurring  in  the  course  of  indi- 
vidual life,  are  not  capable  of  transmission.  I  repeat,  we 
must  not  look  to  mutilations  for  evidence  for  or  against  the 
supposition  that  acquired  characters  are  inherited.  We 
must  look  to  less  abnormal  influences. 

These  readily  divide  themselves  into  two  classes.  The 
first  includes  the  direct  effects  on  the  organism  of  the 
environment — effects,  for  example,  wrought  by  changes  of 
climate,  alteration  of  the  medium  in  which  the  organism 
lives,  and  so  forth.  The  second  comprises  the  effects  of 
use  and  disuse — the  changes  in  the  organism  wrought  by 
the  exercise  of  function. 

Taking  the  former  first,  we  have  the  remarkable  case  of 
Saturnia,  which  was  communicated  to  Darwin  by  Moritz 
Wagner.  Mr.  Mivart  thus  summarizes  it :  "A  number  of 
pupas  were  brought,  in  1870,  to  Switzerland  from  Texas  of 
a  species  of  Saturnia,  widely  different  from  European 
species.  In  May,  1871,  the  moths  developed  out  of  the 
cocoons  (which  had  spent  the  winter  in  Switzerland),  and 
resembled  entirely  the  Texan  species.  Their  young  were 
fed  on  leaves  of  Juglans  regia  (the  Texan  form  feeding  on 
Juglans  nigra),  and  they  changed  into  moths  so  different, 
not  only  in  colour,  but  also  in  form,  from  their  parents, 
that  they  were  reckoned  by  entomologists  as  a  distinct 


164  Animal  Life  and  Intelligence. 

species."*  Professor  Mivart  also  reminds  us  that  English 
oysters  transported  to  the  Mediterranean  are  recorded  by 
M.  Costa  to  have  become  rapidly  like  the  true  Mediterranean 
oyster,  altering  their  manner  of  growth,  and  forming 
prominent  diverging  rays  ;  that  setters  bred  at  Delhi  from 
carefully  paired  parents  had  young  with  nostrils  more 
contracted,  noses  more  pointed,  size  inferior,  and  limbs 
more  slender  than  well-bred  setters  ought  to  have ;  and 
that  cats  at  Mombas,  on  the  coast  of  Africa,  have  short, 
stiff  hair  instead  of  fur,  while  a  cat  from  Algoa  Bay, 
when  left  only  eight  weeks  at  Mombas,  underwent  a  com-  - 
plete  metamorphosis  —  having  parted  with  its  sandy- 
coloured  fur.  Very  remarkable  is  the  case  of  the  brine- 
shrimp  Artemia,  as  observed  and  described  by  Schmanke- 
witsch.  One  species  of  this  crustacean,  Artemia  salina, 
lives  in  brackish  water,  while  A.  milhausenii  inhabits  water 
which  is  much  salter.  They  have  always  been  regarded 
as  distinct  species,  differing  in  the  form  of  the  tail-lobes 
and  the  character  of  the  spines  they  bear.  And  yet,  by 
gradually  altering  the  saltness  of  the  water,  either  of  them 
was  transformed  into  the  other  in  the  course  of  a  few 
generations.  So  long  as  the  altered  conditions  remained 
the  same,  the  change  of  form  was  maintained. 

Many  naturalists  believe  that  climate  has  a  direct  and 
determining  effect  on  colour,  and  contend  or  imply  that  it 
is  hereditary.  Mr.  J.  A.  Allen  correlates  a  decrease  in  the 
intensity  of  colour  with  a  decrease  in  the  humidity  of  the 
climate.  Mr.  Charles  Dixon,  in  his  "Evolution  without 
Natural  Selection,"  says,  "  The  marsh-tit  (Parus  palustris) 
and  its  various  forms  supply  us  with  similar  facts  [illus- 
trative of  the  effects  of  climate  on  the  colours  of  birds]. 
In  warm,  pluvial  regions  we  find  the  brown  intensified; 
in  dry,  sandy  districts  it  is  lighter;  whilst  in  Arctic 
regions  it  is  of  variable  degrees  of  paleness,  until,  in  the 
rigorous  climate  of  Kamschatka,  it  is  almost  white."  Mr. 
Dixon  does  not  think  that  these  changes  are  the  result  of 
natural  selection.  "  Depend  upon  it,"  he  says,  with  some 

*  St.  George  Mivart,  "  On  Truth,"  p.  378. 


Heredity  and  the  Origin  of  Variations.      165 

assurance,*  in  considering  a  different  case,  "  it  is  the  white 
of  the  ptarmigan  (modified  by  climatic  influence)  that  has 
sent  the  bird  to  the  snowy  wastes  and  bare  mountain-tops, 
and  rigorously  keeps  it  there;  not  the  bird  that  has 
assumed,  by  a  long  process  of  natural  selection,  a  white 
dress  to  conceal  itself  in  such  localities."  Professor 
Eimerf  contends  that  in  the  Nile  valley  the  perfectly 
gradual  transition  in  the  colour  of  the  inhabitants  from 
brownish-yellow  to  black  in  passing  from  the  Delta  to  the 
Soudan  is  particularly  conclusive  for  the  direct  influence 
of  climate,  for  the  reason  that  various  races  of  originally 
various  colours  dwell  there. 

Mr.  A.  E.  Wallace  saysj  of  the  island  of  Celebes 
"that  it  gives  to  a  large  number  of  species  and  varieties 
(of  Papilionidse)  which  inhabit  it,  (1)  an  increase  of  size,  and 
(2)  a  peculiar  modification  in  the  form  of  the  wings,  which 
stamp  upon  the  most  dissimilar  insects  a  mark  distinctive 
of  their  common  birthplace."  But  this  similarity  may 
largely,  or  at  least  in  part,  be  due  to  mimicry.  Most 
interesting  and  valuable  are  the  results  of  Mr.  E.  B. 
Poulton's  experiments  on  caterpillars  and  chrysalids.§  They 
show  that  there  is  a  definite  colour-relation  between  the 
caterpillar  (e.g.  the  eyed  hawk-moth,  Smerinthus  ocellatus) 
and  its  food-plant,  adjustable  within  the  limits  of  a  single 
life ;  that  the  predominant  colour  of  the  food-plant  is  itself 
the  stimulus  which  calls  up  a  corresponding  larval  colour ; 
that  there  is  also  a  direct  colour-relation  between  the 
chrysalids  of  the  small  tortoiseshell  butterfly  (Vanessa 
urticcK)  and  the  surrounding  objects,  the  pupae  being  dark 
grey,  light  grey,  or  golden,  according  to  the  nature  and 

*  Op.  cit.,  p.  47.  I  venture  to  say, "  with  some  assurance,"  because  Charles 
Darwin,  who  had  also  considered  this  matter,  writes,  "Who  will  pretend 
to  decide  how  far  the  thick  fur  of  Arctic  animals,  or  their  white  colour,  is 
due  to  the  direct  action  of  a  severe  climate,  and  bow  far  to  the  preservation  of 
the  best-protected  individuals  during  a  long  succession  of  generations  ? " 
("  Animals  and  Plants  under  Domestication,"  p.  415). 

t  "Organic  Evolution,"  English  translation,  p.  88. 

J  "  Contributions  to  Natural  Selection,"  p.  197. 

§  Since  this  was  written,  Mr.  Poulton  has  described  his  results  in  an 
interesting  volume  on  "  The  Colours  of  Animals  " 


1 66  Animal  Life  and  Intelligence. 

colour  of  the  surroundings;  and  that  the  larvae  of  the 
emperor  moth  (Saturnia  carpini]  spin  dark  cocoons  in  dark 
surroundings,  but  white  ones  in  lighter  surroundings. 
These  are  but  samples  of  the  interesting  results  Mr. 
Poulton  has  obtained. 

What  shall  we  say  of  such  cases  ?  Some  of  them  seem 
to  indicate  the  very  remarkable  and  interesting  fact  that 
changes  of  salinity  of  the  medium,  or  changes  of  food,  or 
the  more  general  influence  of  a  special  climate,  may  modify 
organisms  in  particular  and  little-related  ways.  The  larvae 
of  a  Texan  Saturnia  fed  on  a  new  food-plant  develop  into 
images  so  modified  as  to  appear  new  species.  Changes  of 
salinity  of  the  water  modify  one  species  of  Artemia  into 
another.  If  these  be  adaptations,  the  nature  of  the 
adaptation  is  not  obvious.  If  the  new  character  produced 
in  this  way  be  of  utilitarian  value,  where  the  utility  comes 
in  is  not  clear.  The  facts  need  further  confirmation  and 
extension,  which  may  lead  to  very  valuable  results.  Mr. 
Poulton's  observations,  on  the  other  hand,  give  us  evidence 
of  direct  adaptation  to  colour- surroundings.  But  the  effects 
are,  in  the  main,  restricted  to  the  individual.  What  is 
hereditary  is  the  power  to  assume  one  of  two  or  three 
tints,  that  one  being  determined  by  the  surrounding  colour. 
His  experiments  neither  justify  a  denial  nor  involve  an 
assertion  of  the  transmissibility  of  environmental  in- 
fluence. Secondly,  some  of  the  cases  above  cited  seem  to 
show  clearly  that,  under  changed  conditions  of  life,  the 
changes  which  have  been  wrought  in  one  generation  may 
reappear  in  the  next.  But  are  they  inherited  ?  Is  there 
sufficient  evidence  to  show  conclusively  that  the  body-cells 
have  been  modified,  and  have  handed  on  the  modification 
to  the  germ?  Can  we  exclude  the  direct  action  of  the 
more  or  less  saline  water,  or  the  products  of  the  unwonted 
food  on  the  germinal  cells  ?  Can  we  be  sure  that  there  is 
really  a  summation  of  results — that  each  generation  is  not 
affected  de  novo  in  a  similar  manner  ?  No  one  questions 
that  the  individual  is  modifiable,  and  that  such  modifica- 
tion is  most  readily  effected  in  the  early  and  plastic  stages 


Heredity  and  the  Origin  of  Variations.      167 

of  life.  If  each  plastic  embryo  is  moulded  in  turn  by 
similar  influence,  how  can  we  conclusivly  prove  hereditary 
summation  ?  Take  a  case  that  has  been  quoted  in  support 
of  hereditary  modification.  Greyhounds  transported  from 
England  to  the  uplands  of  Mexico  are  unable  to  course, 
owing  to  the  rarity  of  the  atmosphere.  Their  pups  are, 
however,  able  to  run  down  the  fleetest  hares  without 
difficulty.  Now,  this  may  be  due  to  the  fact  that  the  dogs 
acquire  a  certain  amount  of  accommodation  to  a  rare 
atmosphere,  and  hand  on  their  acquired  power  to  their 
offspring,  which  carry  it  on  towards  perfection.  But  it 
may  also  be  due  to  the  fact  that  the  pups,  subject  from  the 
moment  of  birth  to  the  conditions  of  a  rarified  atmosphere, 
are  developed  in  accordance  with  these  conditions. 

Or  take  another  case  that  has  been  brought  forward. 
English  dogs  are  known  in  hot  climates,  like  that  of  India, 
to  degenerate  in  a  few  generations.  Let  us  suppose  that 
these  degenerate  dogs  are  removed  back  to  England,  and 
that  their  pups,  born  in  English  air  and  in  our  temperate 
climate,  are  still  degenerate :  would  not  this,  it  may  be 
asked,  show  that  the  influence  of  climate  on  the  body  is 
inherited  ?  I  do  not  think  that  such  a  case  would  be 
convincing.  For  the  climate  might  well  influence  the 
germ  through  the  body.  The  body  being  unhealthy  and 
degenerate,  the  germ-cells  must,  one  may  suppose,  suffer 
too.  The  degenerate  pup  born  in  England  might  well  owe 
its  degeneracy  to  effects  wrought  upon  the  germinal  cells. 
In  other  words,  such  a  case  would  indicate  some  general 
influence  of  the  environment  (including  the  environing 
body)  on  the  germ.  It  does  not  convince  us  that  particular 
modifications  of  body-cells  as  such  are  transmitted  under 
normal  and  healthy  conditions. 

On  the  whole,  it  seems  to  me  that  the  evidence  we  at 
present  possess  on  this  head  is  not  convincing  or  conclu- 
sive in  favour  of  the  effects  on  the  body  alone  being 
transmitted  to  offspring.  If  cases  can  be  brought  forward 
in  which  there  can  be  no  direct  influence  on  the  germ,  in 
which  elimination  is  practically  excluded,  and  in  which 


1 68  Animal  Life  and  Intelligence. 

there  is  a  gradual  and  increasing  accommodation  of  succes- 
sive generations  of  organisms  to  changed  conditions  which 
remain  constant,  then  such  transmission  will  be  rendered 
probable.  I  do  not  know  that  there  are  observations  of 
this  kind  of  sufficient  accuracy  to  warrant  our  accepting 
this  conclusion  as  definitely  proved. 

Attention  may  here  be  drawn  to  a  peculiar  and  remark- 
able mode  of  influence.  If  a  pure-bred  mare  have  foals  by 
an  ill-bred  sire,  they  will  be  ill-bred.  This  we  can  readily 
understand.  But  if  she  subsequently  have  a  foal  by  a 
perfectly  well-bred  sire,  that  foal,  too,  may  in  some  cases 
be  tainted  by  the  blemish  of  the  previous  sire.  So,  too, 
with  dogs.  If  a  pure-bred  bitch  once  produce  a  mongrel 
litter,  no  matter  how  carefully  she  be  subsequently 
matched,  she  will  have  a  tendency  to  give  birth  to  pups 
with  a  mongrel  taint.  This  subsequent  influence  of  a 
previous  sire  is  a  puzzling  fact.  It  may  be  that  some  of 
the  male  germ-nuclei  are  absorbed,  and  influence  the  germ- 
cells  of  the  ovary.  But  this  seems  an  improbable  solution 
of  the  problem.  It  is  more  likely,  perhaps,  that  in  the 
close  relation  of  mother  and  foetus  during  gestation,  each 
influences  the  other  (how  it  is  difficult  to  say).  On  this 
view  the  bitch  retains  the  influence  of  the  mongrel  puppies 
— is  herself,  in  fact,  partially  mongrelized — and  therefore 
mongrelizes  subsequent  litters.  It  would  not  be  safe,  how- 
ever, to  base  any  far-reaching  conclusions  on  so  peculiar  a 
case,  the  explanation  of  which  is  so  difficult.  At  all  events, 
it  is  impossible  to  exclude  the  possibility  of  direct  action  on 
the  germ,  though  the  particular  nature  of  the  results  of 
such  influence  are  noteworthy. 

We  may  pass  now  to  the  evidence  that  has  been  adduced 
in  favour  of  a  cumulative  effect  in  the  exercise  of  function, 
or  of  the  inheritance  of  the  results  of  use  or  disuse.  Here, 
again,  it  must  be  remembered  that  no  one  questions  the 
effects  of  use  and  disuse  in  the  individual.  What  we  seek 
is  convincing  evidence  that  such  effects  are  inherited. 

Physiologically,  the  effects  of  use  or  disuse  are,  in  the 
main,  effects  on  the  relative  nutrition,  and  hence  on  the 


Heredity  and  the  Origin  of  Variations.      169 

differential  growth  of  organs.  When  an  organ  is  well 
exercised,  there  is  increased  nutrition  and  increased  growth 
of  tissue,  muscular,  nervous,  glandular,  or  other.  When 
an  organ  is,  so  to  speak,  neglected,  there  is  diminished 
blood-supply,  diminished  growth,  and  diminished  functional 
power.  The  development  of  a  complex  activity  would 
necessitate  a  complex  adjustment  of  size  and  efficiency  of 
parts,  involving  a  nice  balance  of  differential  growth  de- 
pendent on  delicately  regulated  nutrition.  What  is  the 
evidence  that  adjusted  nutrition  can  be  inherited  ? 

With  regard  to  man,  there  is  some  evidence  which  bears 
upon  this  subject.  Mr.  Arbuthnot  Lane,  in  his  valuable 
papers  in  the  Journal  of  Anatomy  and  Physiology,  has  shown 
that  certain  occupations,  such  as  shoemaking,  coal-heaving, 
etc.,  produce  recognizable  effects  upon  the  skeleton,  the 
muscular  system,  and  other  parts  of  the  organization.  And 
he  believes  *  that  such  effects  are  inherited,  being  very 
much  more  marked  in  the  third  generation  than  they  were 
in  the  first.  Sir  William  Turner  informed  Professor  Herd- 
man  that,  in  his  opinion,  the  peculiar  habits  of  a  tribe,  such 
as  tree-climbing  among  the  Australians,  or  those  natives 
of  the  interior  of  New  Guinea  whose  houses  are  built  in 
the  upper  branches  of  lofty  trees,  not  only  affect  each 
generation  individually,  but  have  an  intensified  action 
through  the  influence  of  heredity,  t 

Mr.  Francis  Galton's  results  mainly  deal  with  human 
faculty;  and  though  faculty  has  undoubtedly  an  organic 
basis,  I  do  not  propose  to  consider  the  evidence  afforded 
by  instinct,  intelligence,  or  intellectual  faculties  in  this 
chapter.  Mention  should,  however,  be  made  of  the  in- 
teresting results  of  his  study  of  twins.  Twins  are  either 
of  the  same  sex,  in  which  case  they  are  remarkably  alike, 
or  of  different  sexes,  in  which  case  they  are  apt  to  differ 
even  more  widely  than  is  usual  with  brothers  and  sisters. 
The  former  are  believed  to  be  developed  from  one  ovum 

*  See  Journal  of  Anatomy  and  Physiology,  vol.  xxii.  p.  215. 
f  See   Professor    Herdmau's   Inaugural    Address,   Liverpool  Biological 
Society,  1888. 


i  /o  Animal  Life  and  Intelligence. 

which  has  divided  into  two  halves,  each  of  which  has  given 
rise  to  a  distinct  individual ;  the  latter  from  two  different 
ova.  Mr.  Galton  collected  a  large  mass  of  statistics  con- 
cerning twins  of  both  classes.  The  result  of  this  analysis 
seems  to  be  that,  in  the  case  of  "identical  twins,"  the 
resemblances  are  not  superficial,  but  extremely  intimate ; 
that  they  are  not  apt  to  be  modified  to  any  large  extent 
by  the  circumstances  of  life ;  that  where  marked  diversity 
sets  in  it  is  due  to  some  form  of  illness ;  and,  on  the  whole, 
that  innate  tendencies  outmaster  acquired  modifications. 
"Nature  is  far  stronger  than  nurture  within  the  limited 
range  that  I  have  been  careful  to  assign  to  the  latter."  On 
the  other  hand,  speaking  of  dissimilar  twins,  Mr.  Galton 
says,  "I  have  not  a  single  case  in  which  my  correspondents 
speak  of  originally  dissimilar  characters  having  become 
assimilated  through  identity  of  nurture."  "  The  impres- 
sion that  all  this  evidence  leaves  on  the  mind  is  one  of 
some  wonder  whether  nurture  can  do  anything  at  all, 
beyond  giving  instruction  and  professional  training." 
"  There  is  no  escape  from  the  conclusion  that  nature  pre- 
vails enormously  over  nurture  where  the  differences  of 
nurture  do  not  exceed  what  is  commonly  to  be  found  among 
persons  of  the  same  rank  of  society  and  in  the  same 
country."  * 

Combining  the  results  of  Messrs.  Lane  and  Galton, 
we  may  say  that  it  requires  persistent  and  long-continued 
influence  to  modify  the  individual,  and  change,  even  by  a 
little,  the  structure  inherited  or  given  by  nature ;  but  that 
if  this  structure  is  thus  modified,  there  may  be  a  tendency 
for  such  modification  to  increase  by  hereditary  summation 
of  effects.  We  require,  however,  further  and  fuller  observa- 
tions to  render  the  evidence  of  such  hereditary  summation 
to  any  extent  convincing. 

Turning  now  from  the  evidence  afforded  by  man  t  to 

*  Francis  Galton,  "  Inquiries  into  Human  Faculty,"  p.  216. 

f  That  the  epidermis  is  thicker  on  the  palms  of  the  hands  and  the  soles 
of  the  feet  in  the  infant  long  before  birth,  may  be  attributable  to  the  inherited 
effects  of  use  or  pressure.  It  can  hardly  be  held  that  the  thickening  of  the 
skin  in  these  parts  is  of  elimination  value. 


Heredity  and  the  Origin  of  Variations.      171 

that  afforded  by  animals,  we  may  consider  first  that  pre- 
sented by  domesticated  breeds.  They  might  be  expected 
to  afford  exceptionally  good  examples.  Their  modifiability 
and  the  readiness  with  which  they  interbreed  are  two  of 
the  determining  causes  of  their  selection  for  domestication. 
They  have,  moreover,  been  placed  under  new  conditions  of 
life,  and  they  undoubtedly  exhibit  changes  of  structure, 
many  of  which  Darwin  *  regarded  as  attributable  to  the 
effects  of  use  and  disuse.  In  domestic  ducks,  the  relative 
weight  and  strength  of  the  wing-bones  have  been  diminished, 
while  conversely  the  weight  and  strength  of  the  leg-bones 
have  been  increased.  The  bones  of  the  shoulder-girdle  have 
been  decreased  in  weight  and  "the  prominence  of  the  crest 
of  the  sternum,  relatively  to  its  length,  is  also  much  re- 
duced in  all  the  domestic  breeds.  These  changes,"  says 
Darwin,  "have  evidently  been  caused  by  the  lessened  use 
of  the  wings."  The  shoulder-girdle  and  breast-bone  of 
domestic  fowls  have  been  similarly  reduced.  After  a  care- 
ful consideration  of  numerous  facts  concerning  the  brains 
of  rabbits,  Darwin  concluded  that  this  "  most  important 
and  complicated  organ  in  the  whole  organization  is  subject 
to  the  law  of  decrease  in  size  from  disuse."  And  Sir  J. 
Crichton  Browne  has  recently  shown  that,  in  the  wild  duck, 
the  brain  is  nearly  twice  as  heavy  in  proportion  to  the  body 
as  it  is  in  the  comparatively  imbecile  domestic  duck.  In 
pigs,  the  nature  of  the  food  supplied  during  many  genera- 
tions has  apparently  affected  the  length  of  the  intestines ; 
for,  according  to  Cuvier,  their  length  to  that  of  the  body 
in  the  wild  boar  is  as  9  to  1,  in  the  common  domestic  boar 
as  13-5  to  1,  and  in  the  Siam  breed  as  16  to  1.  With 
regard  to  horses,  Darwin  tells  us  that  "  veterinarians  are 
unanimous  that  horses  are  affected  with  spavins,  splints, 
ring-bones,  etc.,  from  being  shod  and  from  travelling  on 
hard  roads,  and  they  are  almost  unanimous  that  a  tendency 
to  these  malformations  is  transmitted." 

These  are  samples  of  the  effects  of  domestication.     It 
has  been  suggested,  however,  that,  quite  apart  from  any 
*  The  instances  cited  are  from  "  Animals  and  Plants  under  Domestication." 


172  Animal  Life  and  Intelligence. 

diminution  from  disuse,  the  reduction  of  size  in  parts  or 
organs  may  be  the  result  of  the  absence  or  cessation  of 
selection.  If  an  organ  be  subject  to  selection,  the  mean 
size  in  adult  creatures  will  be  that  of  the  selected  indi- 
viduals ;  but  if  selection  ceases,  it  will  be  the  mean  of  those 
born.  Let  us  suppose  that  nine  individuals  are  born,  and 
that  the  size  of  some  organ  varies  in  these  from  1,  the 
most  efficient,  to  9,  the  least  efficient.  The  birth-mean  will 
therefore  be,  as  shown  on  the  left-hand  side  of  the  follow- 
ing table,  at  the  level  of  number  5,  four  being  more 
efficient,  and  four  less  efficient.  But  if,  of  these  nine,  six  be 
eliminated,  then  the  mean  of  the  survivals  will  be  as  shown 
on  the  right-hand  side  of  the  table  : — 

i 

2— Survival-mean. 
3 
4\ 
Birth-mean — 5  j 

7  \  Eliminated  individuals. 

s) 

The  result,  then,  of  the  cessation  of  selection  will  be  to 
reduce  the  survival-mean  to  the  birth-mean,  and  that  with- 
out any  necessary  effect  of  disuse.  But  unless  this  be 
accompanied  by  a  tendency  to  diminution  due  to  economy 
of  growth  or  some  other  cause,  this  cannot  produce  any 
well-marked  or  considerable  amount  of  reduction.  I  very 
much  question,  for  example,  whether  the  cessation  of 
selection,  even  with  the  co-operation  of  the  principle  of 
economy  of  growth,  will  adequately  account  for  the  reduc- 
tion to  nearly  one-half  its  original  proportion  of  the  brain 
of  the  duck.  The  subject  will  be  more  fully  discussed, 
however,  in  the  next  chapter. 

There  is  probably  but  little  tendency  for  disused  parts 
to  be  reduced  in  size  through  artificial  selection.  An 
imbecile  duck  does  not  probably  taste  nicer  than  one  with 
bigger  brains.  On  the  other  hand,  the  increase  of  size  in 
organs  may  presumably,  in  certain  cases,  be  increased  by 
selection.  Pigs,  for  example,  have  been  selected  according 


Heredity  and  the  Origin  of  Variations.     173 

to  their  fattening  capacity.  Those  with  longer  intestines, 
and  therefore  increased  absorbent  surface,  may  well  have 
an  advantage  in  this  respect.  Hence,  in  selecting  pigs  for 
fattening,  breeders  may  have  been  unconsciously  selecting 
those  with  the  longest  intestines.  Of  course,  on  this  view, 
the  longer  intestine  must  be  there  to  be  selected,  and  the 
increased  length  must  be  due  to  variation.  But  this  may 
be  all-round  variation  (cause  unknown),  not  variation  in 
one  direction,  the  result  of  increased  function. 

Another  point  that  has  to  be  taken  into  consideration 
is  the  amount  of  individual  increment  or  decrement,  owing 
to  individual  use  or  disuse,  apart  from  any  possible 
summation  of  results. 

Seeing,  then,  that  it  is  difficult  to  estimate  the  amount 
of  purely  individual  increment  or  decrement,  and  that  it  is 
difficult,  if  not  impossible,  to  exclude  the  disturbing  effects 
of  cessation  of  selection  with  economy  of  growth  on  the 
one  hand,  reducing  the  size  of  organs,  and  artificial 
selection  on  the  other  hand,  increasing  the  size  or  efficiency 
of  parts,  it  is  clear  that  such  cases  cannot  afford  convincing 
evidence  that  the  observed  variations  are  the  directly 
inherited  results  of  use  and  disuse.  Indeed,  I  am  not 
aware  of  any  experiments  or  direct  observations  on  animals 
which  are  individually  conclusive  in  favour  of  the  hereditary 
summation  of  functionally  produced  modifications. 

It  may,  however,  be  said — Although  no  absolutely  con- 
vincing experiments  or  observations  are  forthcoming  (for, 
from  the  nature  of  the  case,  it  is  almost  impossible  logically 
to  prove  that  this  interpretation  of  the  facts  is  alone 
possible),  still  there  are  cases  which  are  much  more  readily 
explained  on  the  hypothesis  that  the  effects  of  use  and 
disuse  are  inherited,  than  on  any  other  hypothesis.  But, 
so  far  as  Professor  Weismann  and  his  followers  are  con- 
cerned, such  an  argument  is  wholly  beside  the  question. 
They  are  ready  to  admit  that  inherited  modifications  of  the 
body,  if  they  could  be  proved,  would  render  the  explanation 
of  many  results  of  evolution  much  easier.  It  would,  no 
doubt,  they  say,  be  easier  to  account  for  the  shifting  of  the 


174  Animal  Life  and  Intelligence. 

eye  of  a  flat-fish  from  one  side  of  the  head  to  the  other  on 
the  supposition  that  individual  efforts  were  inherited,  until, 
by  an  hereditary  summation  of  effort,  the  eye  at  last  came 
round.  The  question  is — Are  we  justified  in  accepting  the 
easier  explanation  if  it  be  based  on  a  mere  assumption,  at 
present  unproved,  the  modus  operandi  of  which  is  in- 
explicable ? 

Let  us  consider  very  briefly  these  two  points — first,  the 
"  mere  assumption ;  "  secondly,  "  the  inexplicable  modus 
operandi."  Is  there  any  reason  why  we  should  not  assume 
the  inheritance  of  effects  of  use  or  disuse  as  a  working 
hypothesis,  if  it  is  not  in  opposition  to  any  known  biological 
law,  and  if  it  does  enable  us  to  explain  certain  observed 
phenomena  ?  I  see  no  such  reason.  We  do  not  know 
enough  about  the  causes  of  variation  to  be  rigidly  bound 
by  the  law  of  parcimony.  I  am  not  aware  of  any  biological 
law  that  would  render  the  acceptance  of  this  view  as  a 
provisional  hypothesis  unjustifiable. 

But  how,  it  is  asked,  can  we  accept  it  if  its  modus 
operandi  is  inexplicable  ?  I  question  the  validity  of  this 
argument.  I  fear  our  knowledge  of  organic  nature  is  not 
at  present  so  full  and  exact  as  to  justify  us  in  excluding 
an  hypothesis  because  we  are  not  able  to  give  an  adequate 
answer  to  the  question — How  are  these  effects  produced  ? 
Of  course,  if  it  can  be  shown  that  no  modus  operandi  is 
possible,  there  is  an  end  of  the  matter.  But  who  shall 
dare  thus  to  limit  the  possibilities  of  organic  nature  ? 
And,  if  possible,  then  that  natural  selection  in  which  the 
neo-Darwinians  place  their  sole  trust  would  certainly 
develop  so  advantageous  a  mode  of  influence.  It  is  clear 
that  a  species  sensitive  to  every  shock  of  the  environment 
on  the  organism  would  be  unstable,  and  hence  at  a  dis- 
advantage. But,  on  the  other  hand,  the  ability  to  answer 
by  adaptation  to  long-continued  and  persistent  environ- 
mental influence  or  to  oft-repeated  and  consistent  per- 
formance of  function  would  be  so  distinct  an  advantage  to 
the  species  which  possessed  it,  that,  if  it  lay  within  the 
possibilities  of  organic  nature,  natural  selection,  always,  as 


Heredity  and  the  Origin  of  Variations.      1 75 

we  are  told,  on  the  look  out  for  every  possible  advantage, 
would  assuredly  seize  upon  it  and  develop  it. 

Those  who  believe  in  the  absolute  sway  of  natural 
selection  have  not  at  present  given  any  adequate  answer 
to  the  question — How  are  particular  variations  (e.g.  the 
twisted  skull  of  flat-fish)  produced  ?  They  say  that  con- 
stitutional variations,  which  are  alone  inheritable,  are  due 
to  variations  in  the  germs.  When  asked  how  these 
variations  are  produced,  they  are  forced  to  reply — We 
cannot  say.  But  when  it  is  suggested  that  they  may  be 
in  some  unknown  way  transmitted  to  the  germ  from  the 
body,  they  are  up  in  arms,  and  exclaim — You  have  no 
right  to  believe  that,  or  ask  us  to  believe  it,  unless  you  can 
tell  us  plainly  how  the  effect  is  produced.  Unable  them- 
selves to  give  the  modus  operandi  of  the  origin  of  particular 
variations,  they  demand  the  exact  modus  operandi  from 
those  who  suggest  that  variations  may  arise  through  this 
mode  of  influence  of  the  body  on  the  germ. 

We  shall  have  to  consider  this  question  from  a  more 
general  standpoint  in  the  next  chapter  on  "  Organic  Evolu- 
tion." We  may  now  very  briefly  summarize  some  of  the 
results  we  have  reached  in  this  chapter. 

The  ova  and  sperms  are  specially  differentiated  cells 
which  have,  in  the  division  of  labour,  retained  and  empha- 
sized the  function  of  developmental  reproduction. 

There  is  a  continuity  of  such  cells.  The  cells  which 
become  ova  or  sperms  have  never  become  differentiated  into 
anything  else. 

Hereditary  similarity  is  due  to  the  fact  that  parents  and 
offspring  are  derived  eventually  from  the  same  germinal  cells. 

Variation  in  the  existing  world  is  partly  due  to  sexual 
union.  But  if  there  be  mere  admixture,  new  characters 
cannot  arise  in  this  way,  nor  can  old  characters  be 
strengthened  beyond  the  existing  maximum. 

Some  mode  of  organic  combination  (analogous  to 
chemical  combination)  might  afford  an  explanation  of  the 
occurrence  of  new  variations  and  the  increase  of  existing 
characters. 


176  Animal  Life  and  Intelligence. 

In  the  protozoa  there  may  be  a  summation  of  the  effects 
of  the  environment  in  succeeding  generations. 

There  is  no  convincing  evidence  that  in  the  metazoa 
special  modifications  of  the  body  so  influence  the  germ 
as  to  become  hereditary. 

But  there  is  no  reason  why  such  influence  should  not 
be  assumed  as  a  provisional  hypothesis. 


CHAPTER  VI. 

ORGANIC    EVOLUTION. 

IT  is  difficult  to  realize  the  wealth,  the  variety,  the  diversity, 
of  "animal  life."  Even  if  we  endeavour  to  pass  in  review 
all  that  we  have  seen  in  woodland  and  meadow,  in  pond 
or  pool,  in  the  air,  on  the  earth,  in  the  waters,  in  temperate 
or  tropical  regions ;  even  when  we  try  to  remember  the 
results  of  all  anatomical  and  microscopic  investigation  dis- 
playing new  wonders  and  new  diversities  hidden  from 
ordinary  and  unaided  vision ;  even  when  we  call  to  mind 
the  multifarious  contents,  recent  and  fossil,  of  all  the 
natural  history  museums  we  have  ever  visited,  and  throw 
in  such  mental  pictures  as  we  have  formed  of  all  the  diverse 
adaptations  we  have  read  about  or  heard  described ; — even 
so  we  cannot  but  be  conscious  that  not  one-tenth,  not  one- 
hundredth,  part  of  the  diversity  and  variety  of  animal  life 
has  passed  before  our  mental  vision  even  in  sample.  It  is 
said  that  our  greatest  living  poet  once,  when  a  young  man, 
left  his  companions  to  gaze  into  the  waters  of  a  clear,  still 
pool.  "  What  an  imagination  God  has  !  "  he  said,  as  he 
rejoined  his  friends.  Fit  observation  for  the  poet,  whose 
sensitive  nature  must  be  keenly  alive  to  the  varied  endow- 
ments which  Nature  has  lavishly  showered  upon  her 
animate  children. 

Certain  it  is  that  words,  mere  words,  can  never  present, 
though  they  may  aid  in  recalling,  an  adequate  picture  of 
either  the  wealth  or  the  beauty  of  animal  life.  Fortunately 
for  those  who  visit  London  (and  who  nowadays  does  not  ?), 
we  have,  in  our  national  collection  in  South  Kensington, 
the  means  of  getting  some  insight  into  the  wealth  of  life. 

N 


178  Animal  Life  and  Intelligence. 

And  much  is  being  done  there  to  aid  the  imagination  and 
to  facilitate  study  for  those  who  are  not  professed  students. 
Many  of  the  birds  are  now  to  be  seen  set  in  their  natural 
surroundings,  with  their  life-history  illustrated.  Our 
frontispiece  is  taken  from  one  of  these  cases.  And  this 
admirable  system  will,  no  doubt,  so  far  as  space  permits, 
be  extended ;  and,  perhaps,  dramatic  incidents  may  be 
introduced,  like  those  (notably  in  the  life  of  heron  and 
hawk)  which  form  so  marked  a  feature  in  the  little  museum 
at  Exeter.  Anything  which  leads  us  to  understand  the  life 
of  animals,  and  to  go  forth  and  study  it  for  ourselves,  has 
an  educational  value. 

In  our  National  Museum,  again,  much  is  being  wisely 
done  to  illustrate  the  diversity  and  variety  of  structure 
and  the  principles  that  underlie  them.  Observe,  as  you 
enter  the  central  hall,  the  case  containing  stuffed  specimens 
of  ruffs  (Machetes  pugnax).  Among  the  young  autumn 
birds  there  is  not  much  difference  between  males  and 
females,  the  male  being  distinguished  chiefly  by  its  some- 
what larger  size.  Nor  do  the  old  birds,  male  and  female, 
differ  much  during  the  winter  months.  But  in  pairing- 
time,  May  and  June,  the  females  are  somewhat  richer  in 
colour ;  while  the  males  not  only  don  the  ruff  to  which  the 
bird  owes  its  popular  name,  but  develop  striking  colour- 
tints.  Among  different  individuals  it  will  be  seen  that  the 
colour-variation  is  tolerably  wide ;  but  the  same  individual 
keeps  strictly,  we  are  told,  in  successive  seasons,  to  the 
same  summer  dress.  Note,  next,  in  a  bay  to  the  right, 
the  great  variety  of  form,  ornamentation,  and  colouring 
among  the  molluscan  shells  there  exhibited.  Observe  that 
the  rich  colours  are  often  hidden  during  life  by  the  dull 
epidermis.  Half  an  hour's  attentive  study  of  these  varied 
molluscan  forms  will  give  a  better  idea  of  the  beauty  and 
diversity  of  these  life-products  than  pages  of  mere  de- 
scription. 

Pass  on,  too,  to  note,  in  a  further  bay  to  the  right,  the 
extraordinary  modifications  of  the  antenna,  or  feeler,  in 
insects.  There  is  the  long,  whip-like  form  in  the  locust ; 


Organic  Evolution.  179 

the  clubbed  whip  in  the  ant-lion  and  the  butterfly;  the 
feathered  form  in  certain  moths  and  flies ;  the  hooked  form 
characteristic  of  the  sphinx-moths ;  the  many-leaf  form 
in  the  lamellicorn  beetles,  like  the  cockchafer;  and  the 
feathered  plate  of  other  beetles.  Equally  wonderful  are 
the  diverse  developments  of  the  mouth-organs  of  insects, 
the  spiral  tube  of  the  butterfly  or  moth,  the  strong  jaws  of 
the  great  beetles,  the  lancets  of  the  gnat,  the  sucking-disc 
of  the  fly, — all  of  them  special  modifications  of  the  same 
set  of  structures.  Then,  in  the  same  bay,  note  some  of 
the  striking  differences  between  the  males  and  females 
of  certain  insects.  In  some  there  is  an  extraordinary 
difference  in  size  (e.g.  the  locust  Xiphocera,  and  the  moth 
Attacus) ;  in  others,  like  the  stag-beetle,  it  is  the  size  of 
the  jaws  that  distinguishes  the  males ;  in  others,  again, 
the  most  notable  differences  are  in  the  length,  development, 
or  complexity  of  the  antennae,  or  feelers  ;  in  some  beetles 
the  males  have  great  horns  on  the  head  or  thorax ;  while 
in  many  butterflies  it  is  in  richness  of  colour  that  the 
difference  chiefly  lies — the  brilliant  green  of  the  Ornithoptera 
there  exhibited  contrasting  strongly  with  the  sober  brown 
of  his  larger  mate. 

The  fact  that  the  special  characteristics  of  the  male, 
which  we  have  seen  to  be  variable  in  the  ruff,  are  also 
variable  among  insects,  is  well  exemplified  in  the  case  of 
the  stag-beetle,  in  some  males  of  which  the  mandibles  are 
far  larger  than  in  others.  This  is  shown  in  Fig.  22,  which 
is  copied  from  the  series  displayed  in  the  British  Museum, 
by  the  kind  permission  of  Professor  Flower. 

Crossing  the  hall  to  where  the  vertebrate  structures  are 
displayed,  the  development  of  hair,  of  feathers,  of  teeth, 
the  modifications  of  the  skull  and  of  legs,  wings,  and  fins 
are  being  exemplified.  Note  here  and  elsewhere  the  special 
adaptations  of  structure,  of  which  we  may  select  two 
examples.  The  first  is  that  seen  in  the  Balistes,  or  trigger- 
fish.  The  anterior  dorsal  fin  is  reduced  to  three  spines,  of 
which  that  which  lies  in  front  is  a  specially  modified 
weapon  of  defence,  while  that  which  follows  it  is  the  so- 


180  Animal  Life  and  Intelligence. 


Organic  Evolution.  181 

called  trigger.  These  two  are  so  hinged  to  the  underlying 
interspinous  bones  and  so  related  to  each  other  that,  when 
once  the  defensive  spine  in  front  is  erected,  it  cannot  be 
forced  down  until  the  trigger  is  lowered.  The  second 
example  of  special  adaptation  is  well  displayed  in  specimens 
of  the  mud-tortoise  Trionyx.  Between  the  last  vertebra 
of  the  neck  and  the  first  fixed  vertebra  of  the  dorsal  series 
is  a  beautiful  hinge-joint,  enabling  the  neck  to  be  bent 
back,  S-fashion,  when  the  creature  withdraws  its  head 
within  the  carapace.  These  are  only  one  or  two  particular 
instances  of  what  any  one  who  will  visit  the  National 
Museum  may  see  for  himself  admirably  displayed  and 
illustrated. 

No  one  can,  one  would  suppose,  pass  through  the 
galleries  in  Cromwell  Eoad  and  remain  quite  insensible  to 
the  beauties  of  animal  life.  Beauty  of  form  and  beauty  of 
colour  are  conspicuously  combined  in  many  species  of  birds 
and  insects.  And  much  of  this  colour-beauty  and  splendid 
iridescence  is  known  to  be  due  to  minute  scales,  to  thin 
films  of  air  or  fluid,  and  to  microscopically  fine  lines 
developed  upon  scales  or  feathers.  But  there  is  one  phase 
of  beauty  which  cannot  be  exhibited  in  the  museum — the 
beauty  that  comes  of  life  as  opposed  to  death.  For  this 
we  must  go  out  into  the  free  air  of  nature,  where  the 
animals  not  only  have  lived,  but  are  still  instinct  with  the 
glow  of  life,  and  where  the  silence  of  the  museum  galleries 
is  replaced  by  the  song  of  birds  and  the  hum  of  insect- 
wings. 

How  have  this  wealth,  this  diversity,  this  beauty,  this 
manifold  activity,  which  we  summarize  under  the  term 
"  animal  life,"  been  produced  ? 

If  we  answer  this  question  hi  a  word — the  word  "  evolu- 
tion "  * — we  must  remember  that  this  word  merely  ex- 
presses our  belief  in  a  general  fact;  and  we  must  not 

*  It  is  beyond  the  scope  of  this  book  to  give  the  evidences  of  evolution. 
Such  evidence  from  embryology,  from  distribution,  and  from  palaeontology, 
is  now  abundant.  For  palseontological  evidence,  see  Nicholson's  "  Manual 
of  Palaeontology,"  3rd  edit.,  especially  the  second  volume  on  "  Vertebrates," 
by  E.  Lydekker. 


1 82  Animal  Life  and  Intelligence. 

forget  that  many  questions  remain  behind,  all  centering 
round  that  little  question,  to  which  an  adequate  answer  is 
so  difficult  to  give,  the  question — How  ?  Reduced  to  its 
simplest  expression,  the  doctrine  of  evolution  merely  states 
that  the  animal  world  as  it  exists  to-day  is  naturally 
developed  out  of  the  animal  world  as  it  existed  yesterday, 
and  will  in  turn  develop  into  the  animal  world  as  it  shall 
exist  to-morrow.  This  is  the  central  belief  of  the  evolu- 
tionist. No  matter  what  moment  in  the  past  history  of 
life  you  select,  the  life  at  that  moment  was  in  the  act  of 
insensibly  passing  from  the  previous  towards  a  future  con- 
dition. Then  at  once  arises  the  question — Does  life  remain 
the  same  yesterday,  to-day,  and  to-morrow  ?  A  thousand 
indubitable  facts  at  once  make  answer — No  !  Underlying 
the  law  of  continuity  there  is  a  law  of  change.  Life  to-day 
is  not  what  it  was  yesterday,  nor  will  it  be  to-morrow  the 
same  as  to-day.  What,  then,  is  the  nature  of  this  change  ? 
If  it  be  replied  that  the  change  must  be  either  for  the 
better  or  the  worse,  we  shall  have  to  answer  the  further 
question — Better  or  worse  in  what  respects  ? 

Let  us  narrow  our  view  from  the  contemplation  of  life 
as  a  whole  to  the  more  particular  consideration  of  an 
organism  as  one  of  its  constituent  units.  The  individual 
life  of  that  organism  depends  on  (some  would  say  consists 
in)  its  ceaseless  adaptation  to  surrounding  circumstances. 
The  circumstances  remaining  the  same,  or  only  varying 
within  constant  limits,  the  adaptation  may  be  more  or  less 
perfect.  A  change  in  the  direction  of  more  perfect  adapta- 
tion will  be  a  change  for  the  better,  a  tendency  to  less 
perfect  adaptation  will  be  a  change  for  the  worse. 

But  the  relation  of  an  organism  to  its  circumstances  or 
environment  is  itself  subject  to  change.  The  environment 
itself  may  alter,  or  the  organism  may  be  brought  into  relation 
with  a  new  environment.  We  have  to  consider  not  only 
the  changes  in  an  organism  in  the  direction  of  more  or 
less  perfect  adaptation  to  its  environment,  but  also  changes 
in  the  environment.  These  changes  are  in  the  direction 
of  increased  simplicity  or  of  increased  complexity.  So 


Organic  Evolution.  183 

that  we  may  say  that  the  modification  of  life  is  in  the 
direction  of  more  or  of  less  complete  adaptation  to  simpler 
or  to  more  complex  conditions.  Where  the  adaptation 
advances  to  more  complex  conditions,  we  speak  of  elabora- 
tion ;  where  it  retrogrades  to  less  complex  conditions,  we 
speak  of  degeneration ;  but  both  fall  under  the  head  of 
evolution  in  its  more  general  sense.  Viewed  as  a  whole, 
there  can  be  little  doubt  that  the  general  tendency  of 
evolution  is  towards  more  complete  adaptation  to  more 
diverse  and  complex  environment.  And  this  tendency  is 
accompanied  by  a  general  increase  of  differentiation  and 
of  integration ;  of  differentiation  whereby  the  constituent 
elements  of  life,  whether  cells,  tissues,  organs,  organisms, 
or  groups  of  organisms,  become  progressively  more 
specialized  and  more  different  from  one  another ;  of 
integration  whereby  these  elements  become  progressively 
more  interdependent  one  on  the  other.  We  may  con- 
veniently sum  up  the  tendency  towards  more  perfect 
adaptation  to  more  complex  circumstances  in  the  word 
progress;  the  tendency  to  differentiation  in  the  word 
individuality;  and  the  tendency  to  integration  in  the 
word  association. 

Nobody  now  doubts  the  propositions  thus  briefly  sum- 
marized, and  it  is  therefore  unnecessary  to  bring  forward 
evidence  in  their  favour. 

We  may  pass,  then,  to  the  question — How  ?  Evolution 
being  continuity,  associated  with  change,  tending  in  certain 
directions,  and  accompanied  by  certain  processes,  how  has 
it  been  effected  ?  What  are  its  methods  ? 

'    L/ 

Natural  Selection. 

Natural  selection  claims  a  foremost  place.  We  have 
already  devoted  a  chapter  to  its  consideration.  Animals 
vary ;  more  are  born  than  can  survive  to  procreate  their 
kind ;  hence  a  struggle  for  existence,  in  which  the  weaker 
and  less  adapted  are  eliminated,  the  stronger  and  better 
adapted  surviving  to  continue  the  race. 


184  Animal  Life  and  Intelligence. 

It  is  scarcely  possible  to  over-estimate  what  Darwin's 
labour  and  genius  have  done  for  the  study  of  animal  life. 
Through  Darwin's  informing  spirit,  biology  has  become  a 
science.  But  now  we  must  be  on  our  guard.  So  long  as 
natural  selection  was  whining  its  way  to  acceptance,  every 
application  of  the  theory  had  to  be  made  with  caution,  and 
was  subjected  to  keen,  if  sometimes  ignorant,  criticism. 
Now  there  is,  perhaps,  some  danger  lest  it  should  suffer 
the  Nemesis  of  triumphant  creeds,  and  be  used  blindly  as 
a  magic  formula. 

First,  we  should  be  careful  not  to  use  the  phrase,  "  of 
advantage  to  the  species,"  vaguely  and  indefinitely,  but 
should  in  all  cases  endeavour  clearly  to  indicate  wherein 
lies  the  particular  advantage,  and  how  its  possession 
enables  the  organism  to  escape  elimination ;  next,  we  must 
remember  that  the  advantage  must  be  immediate  and 
present,  prospective  advantage  being,  of  course,  inoperative ; 
then  we  must  endeavour  to  show  that  the  advantage  is 
really  sufficient  to  decide  the  question  of  elimination  or 
non-elimination ;  lastly,  we  must  distinguish  between 
indiscriminate  and  differential  destruction,  between  mere 
numerical  reduction  by  death  or  otherwise  and  selective 
elimination. 

(1)  In  illustration  of  the  first  point,  we  may  select  a 
passage  from  the  writings  of  even  so  great  a  biologist  as 
Professor  Weismann.  As  is  well  known,  Professor  Weis- 
mann  believes  that  senility  and  death  are  no  part  of  the 
natural  heritage  of  animal  life,  but  have  been  introduced 
among  the  metazoa  on  utilitarian  grounds.  In  his  earlier 
papers,  he  attributed  the  introduction  of  death,  and  the 
tissue -degeneration  that  precedes  it,  to  the  direct  action  of 
natural  selection.*  More  lately,  he  attributes  it  to  the 
cessation  of  selection. f  Concerning  this  later  view,  we 
shall  have  somewhat  to  say  presently ;  we  may  now  con- 
sider the  former  as  an  example  of  too  indefinite  a  use  of 
such  phrases  as  "of  advantage  to  the  species."  "  Worn- 
out  individuals,"  says  Professor  Weismann,  "are  not  only 

*  Weismann,  "  Essays  on  Heredity,"  p.  24.  t  Ibid.  p.  140. 


Organic  Evolution.  185 

valueless  to  the  species,  but  they  are  even  harmful,  for 
they  take  the  places  of  those  which  are  sound.  Hence,  by 
the  operation  of  natural  selection,  the  life  of  our  hypo- 
thetically  immortal  individual  would  be  shortened  by  the 
amount  which  was  useless  to  the  species.  It  would  be 
reduced  to  a  length  which  would  afford  the  most  favourable 
conditions  of  existence  of  as  large  a  number  as  possible  of 
vigorous  individuals  at  the  same  time."  This  may  be  so, 
but,  as  it  stands,  the  modus  operandi  is  not  given,  and  is 
not  obvious.  We  start  with  a  hypothetically  immortal 
metazoon.  Barring  accidents,  it  will  go  on  existing  in- 
definitely. But  you  cannot  bar  accidents  for  an  indefinite 
time;  hence,  the  longer  the  individual  lives,  the  more 
defective  and  crippled  it  becomes.  There  is  neither  natural 
decay  nor  natural  death  here.  The  organism  is  gradually 
crippled  through  accident  and  injury.  But  the  crippled 
individuals  are  harmful  to  the  species,  because  they  take 
the  places  of  those  which  are  sound.  Therefore,  says 
Professor  Weismann,  natural  decay  and  death  step  in  to 
take  them  off  before  they  have  time  to  become  cripples. 
Now,  the  point  I  wish  to  notice  is  that  there  is  no  definite 
statement  how  or  why  natural  decrepitude  should  thus 
be  introduced.  We  must  remember  that  it  is  not  until  a 
late  stage  in  evolution  that,  through  the  association  of  its 
members,  groups  of  organisms  compete  with  other  groups. 
In  the  earlier  stages,  when  we  must  suppose  decrepitude 
and  death  to  arise  on  Professor  Weismann's  hypothesis,  the 
law  of  the  struggle  for  existence  is — each  for  himself 
against  all.  The  question,  therefore,  is — What  advantage 
to  the  individual  is  there  in  natural  decay  and  death  to 
enable  it,  through  the  possession  of  these  attributes,  to 
escape  elimination  ?  Surely  none  as  such.  At  the  same 
time,  it  is  quite  conceivable  that  natural  decay  and  death 
may  be  the  penalty  the  individual  has  to  pay  for  increased 
strength  and  vitality  in  the  early  stages  of  life.  This, 
probably,  was  Professor  Weismann's  meaning.  But,  if  so, 
it  would  surely  have  been  better  to  state  the  matter  in 
such  a  way  as  to  lay  the  chief  stress  on  the  really  important 


1 86  Animal  Life  and  Intelligence. 

feature,  and  to  say  that,  through  natural  selection,  those 
individuals  have  survived  which  exhibited  predominant 
strength  and  vitality  for  a  shortened  period,  even  at  the 
expense  of  natural  decay  and  death.  The  increased  life- 
power,  not  the  seeds  of  decay  and  death,  was  that  which 
natural  selection  picked  out  for  survival,  or  rather  that 
which  elimination  allowed  to  survive. 

In  such  ways — a  short  life  with  heightened  activity 
being  of  advantage  to  some  forms,  a  more  prolonged 
existence  at  a  lower  level  of  vitality  being  essential  to 
others — natural  selection  may  have  determined  in  some 
degree  the  relative  longevity  of  different  organisms.  That 
it  caused  the  introduction  of  senility  as  a  preparation  for 
death  is  a  less  tenable  hypothesis. 

And  here  we  may  note,  in  passing,  that  in  using  the 
phrase,  "of  advantage  to  the  race  or  species,"  we  must 
steadily  bear  in  mind  the  fact  that  it  is  with  individuals 
that  the  process  of  elimination  deals.  In  the  individual  it 
is  that  every  modification  must  make  good  its  claim  to 
existence  and  transmission.  Where  the  principle  of  asso- 
ciation for  mutual  benefit  obtains,  as  in  the  case  of  social 
insects,  it  is  still  the  individual  that  must  resist  elimina- 
tion. Self-sacrifice,  whether  conscious  or  unconscious, 
must  not  be  carried  so  far  as  to  lead  to  the  elimination  of 
the  self-sacrificing  individual,  for  in  this  event  it  cannot 
but  defeat  its  own  ends.  Within  these  limits,  self-sacrifice 
is  of  advantage,  as  in  the  case  of  parental  self-sacrifice,  in 
that  it  enables  certain  other  individuals  to  escape  elimina- 
tion. We  should  endeavour,  then,  not  to  use  the  phrase, 
"  of  advantage  to  the  species,"  vaguely  and  indefinitely,  but 
to  indicate  in  what  particular  ways  certain  individuals  are 
to  be  so  advantaged  as  to  escape  the  Nemesis  of  elimination. 

(2)  The  second  point  that  I  mentioned  above  scarcely 
needs  exemplification.  That  the  advantage  which  enables 
an  organism  to  escape  elimination  must  be  present  and 
existent,  not  merely  prospective,  is  obvious.  Still,  the 
mistake  is  sometimes  made.  I  have  heard  it  stated  that 
feathers  were  evolved  for  the  sake  of  flight.  But  clearly, 


Organic  Evolution.  187 

unless  the  wing  sprang  into  existence  already  sufficiently 
developed  for  flight,  this  would  be  impossible.  The  same 
is  true  of  the  first  stages  of  many  structures  which  could 
not  be  of  service  for  the  purpose  and  use  to  which  they 
were  subsequently  turned.  Not  impossibly,  the  earliest 
"wings"  were  for  diving,  and  flight  was,  so  to  speak,  an 
after-thought.  Undoubtedly,  structures  which  have  been 
fostered  under  the  wing  of  one  form  of  advantage  have 
been  subsequently  applied  to  new  purposes,  and  fostered 
through  new  modes  of  adaptation.  Teeth,  for  example,  are 
probably  modified  scales,  such  as  are  found  in  the  thorn- 
back  skate.  But  the  early  development  of  these  scales 
could  have  had  no  reference  to  their  future  application  to 
purposes  subservient  to  alimentation. 

Again,  such  and  such  a  structure  is  sometimes  spoken 
of  as  a  "  prevision  against  emergencies."  In  his  interest- 
ing and  valuable  work  on  "  The  Colours  of  Animals," 
for  example,  Mr.  E.  B.  Poulton  says,  "Dimorphism  [in 
the  larvae  of  butterflies  and  moths]  is  also  valuable  in 
another  way :  the  widening  range  of  a  species  may  carry  it 
into  countries  in  which  one  of  its  forms  may  be  especially 
well  concealed,  while  in  other  countries  the  other  form  may 
be  more  protected.  Thus  a  dimorphic  form  is  more  fully 
provided  against  emergencies  than  one  with  only  a  single 
form."  And  after  giving,  as  an  example,  the  fact  that  the 
convolvulus  hawk-moth  has  a  browner  and  a  greener  form 
of  caterpillar,  of  which  the  browner  is  more  prevalent 
under  European  conditions,  and  the  greener  under  those 
which  obtain  in  the  Canary  Islands,  Mr.  Poulton  adds, 
"  This  result  appears  to  have  been  brought  about  by  the 
ordinary  operation  of  natural  selection,  leading  to  the 
extermination  of  the  less-protected  variety."  Now,  I  do 
not  mean  for  one  moment  to  imply  that  so  careful  and  able 
a  naturalist  as  Mr.  Poulton  believes  that  any  character  has 
been  evolved  through  natural  selection  in  prevision  for 
future  emergencies.  But  I  do  think  that  his  statement  is 
open  to  this  criticism. 

(3)  It  is  sometimes  said,  in  bold  metaphor,  that  natural 


1 88  Animal  Life  and  Intelligence. 

selection  is  constantly  on  the  watch  to  select  any  modifica- 
tion, however  slight,  which  is  of  advantage  to  the  species. 
And  it  is  true  that  elimination  is  ceaselessly  operative. 
But  it  is  equally  certain  that  the  advantage  must  be  of 
sufficient  value  to  decide  the  question  whether  its  possessor 
should  be  eliminated  or  should  escape  elimination.  If  it 
does  not  reach  this  value,  Natural  Selection,  watch  she 
never  so  carefully,  can  make  no  use  of  it.  Elimination 
need  not,  however,  be  to  the  death ;  exclusion  from  any 
share  in  continuing  the  species  is  sufficient.  To  breed  or 
not  to  breed,  that  is  the  question.  Any  advantage  affect- 
ing this  essential  life-function  will  at  once  catch  the  eye  of 
a  vigilant  natural  selection.  But  it  must  be  of  sufficient 
magnitude  for  the  machinery  of  natural  selection  to  deal 
with.  That  machinery  is  the  elimination  of  a  certain 
proportion  of  the  individuals  which  are  born.  Which  shall 
be  eliminated,  and  which  shall  survive,  depends  entirely  on 
the  way  in  which  the  individuals  themselves  come  out  in 
life's  competitive  examination.  The  manner  in  which  that 
examination  is  conducted  is  often  rude  and  coarse,  too  rough- 
and-ready  to  weigh  minute  and  infinitesimal  advantages. 

What  must  be  the  value  of  a  favourable  or  advantageous 
modification  to  decide  the  question  of  elimination,  to  make 
it  an  available  advantage,  must  remain  a  matter  of  conjec- 
ture. It  will  vary  with  the  nature  and  the  pressure  of  the 
eliminative  process.  And  perhaps  it  is  scarcely  too  much 
to  say  that,  at  present,  we  have  not  observational  grounds 
on  which  to  base  a  reliable  estimate  in  a  single  instance. 
We  must  not  let  our  conviction  of  its  truth  and  justice 
blind  us  to  the  fact  that  natural  selection  is  a  logical 
inference  rather  than  a  matter  of  direct  observation.  A 
hundred  are  born,  and  two  survive ;  the  ninety-eight  are 
eliminated  in  the  struggle  for  existence ;  we  may  therefore 
infer  that  the  two  escaped  elimination  in  virtue  of  their 
possession  of  certain  advantageous  characters.  There  is 
no  flaw  in  the  logic  that  has  thus  convinced  the  world  that 
natural  selection  is  a  factor  in  evolution.  But  by  what 
percentage  of  elimination-marks  the  second  of  the  two 


Organic  Evolution.  189 

successful  candidates  beats  the  senior  on  the  list  of  failures 
we  do  not  know.  We  can  only  see  that,  on  the  hypothesis 
of  natural  selection,  it  must  have  been  sufficiently  ap- 
preciable to  determine  success  or  failure. 

(4)  And  then,  to  come  to  our  fourth  point,  we  must 
remember  that,  apart  from  the  differentiating  process  of 
elimination,   there    is  much    fortuitous    destruction.      A 
hundred  are  born,  and  but  two  survive.    But  of  the  ninety- 
eight  which   die,  and  fail  to  procreate,   how  many  are 
eliminated,  how  many  are  fortuitously  destroyed,  we  do 
not  find  it  easy  to  say.     And  indiscriminate  destruction 
gets  rid  of  good,  bad,  and  indifferent  alike.     It  is  a  mistake 
to  say  that  of  the  hundred  born  the  two  survivors  are 
necessarily  the  very  best  of  the  lot.     It  is  quite  possible 
that  indiscriminate  destruction  got  rid  of  ninety  of  all  sorts, 
and  left  only  ten  subject  to  the  action  of  a  true  elimina- 
tion.    "  In  the  majority  of  birds,"  says  Professor  Weis- 
mann,  "  the  egg,  as  soon  as  it  is  laid,  becomes  exposed  to 
the  attacks  of  enemies;   martens  and  weasels,  cats  and 
owls,  buzzards  and  crows,  are  all  on  the  look  out  for  it. 
At  a  later  period,  the  same  enemies  destroy  numbers  of  the 
helpless  young,  and  in  winter  many  succumb  in  the  struggle 
against  cold  and  hunger,  or  to  the  numerous  dangers  which 
attend  migration  over  land  and  sea — dangers  which  decimate 
the  young  birds."     There  is  here,  first,  a  certain  amount 
of  fortuitous  destruction ;  secondly,  some  selection  applied 
to  the  eggs ;  thirdly,  a  selection  among  the  very  young 
nestlings ;   and,   fourthly,   a   selection   among  the  young 
migratory  birds.     What  may  be  the  proportion  of  elimina- 
tion to  destruction   at  each   stage  it  is  difficult  to   say. 
Among  the  eggs  and  fry  of  fishes  fortuitous  destruction 
probably  very  far    outbalances    the  truly  differentiating 
process. 

Panmixia  and  Disuse. 

We  may  now  pass  on  to  consider  shortly  some  of  the 
phenomena  of  degeneration,  and  the  dwindling  or  dis- 
appearance of  structures  which  are  no  longer  of  use. 


190  Animal  Life  and  Intelligence. 

Many  zoologists  believe,  or  until  lately  have  believed, 
that  disuse  is  itself  a  factor  in  the  process.  Just  as  the 
well-exercised  muscle  is  strengthened,  so  is  the  neglected 
muscle  rendered  weak  and  flabby.  Until  recently  it  was 
generally  held  that  the  effects  of  such  use  or  disuse  are 
inherited.  But  now  Professor  Weismann  has  taught  us, 
if  not  to  doubt  ourselves,  at  least  to  admit  that  doubt  is 
permissible.  On  the  older  view,  the  gradual  dwindling  of 
unused  parts  was  readily  comprehensible.  But  now,  if  Pro- 
fessor Weismann  is  right,  we  must  seek  another  explanation 
of  the  facts ;  and,  in  any  case,  we  may  be  led  to  recognize 
other  factors  (than  that  of  disuse  alone)  in  the  process. 

Professor  Weismann  regards  panmixia,  or  free  inter- 
crossing, when  the  preserving  influence  of  natural  selection 
is  suspended,  as  the  efficient  cause  of  a  reduction  or  de- 
terioration in  the  organ  concerned.  And  Mr.  Romanes 
had,  in  England,  drawn  attention  to  the  fact  that  the 
"  cessation  of  natural  selection "  would  lead  to  some 
dwindling  of  the  organ  concerned,  since  it  was  no  longer 
kept  up  to  standard.  In  illustration  of  his  panmixia,  Pro- 
fessor Weismann  says,  "A  goose  or  duck  must  possess 
strong  powers  of  flight  in  the  natural  state,  but  such 
powers  are  no  longer  necessary  for  obtaining  food  when  it 
is  brought  into  the  poultry-yard,  so  that  a  rigid  selection 
of  individuals  with  well-developed  wings  at  once  ceases 
among  its  descendants.  Hence,  in  the  course  of  genera- 
tions, a  deterioration  of  the  organs  of  flight  must  neces- 
sarily ensue,  and  the  other  members  and  organs  of  the 
bird  will  be  sensibly  affected."  *  And,  again,  "  As  at  each 
stage  of  retrogressive  transformation  individual  fluctuations 
always  occur,  a  continued  decline  from  the  original  degree 
of  development  will  inevitably,  although  very  slowly,  take 
place,  until  the  last  remnant  finally  disappears."  f  Now, 
I  think  it  can  be  shown  that  panmixia,  or  the  cessation  of 
selection,  alone  cannot  affect  much  reduction.  It  can  only 

*  Weismann,  "  Essays  on  Heredity,"  p.  90. 

t  Ibid.  p.  292.     See  also  a  discussion  in  Nature,  in  which  Mr.  Romanes 
and  Professor  Ray  Lankester  took  part,  beginning  vol.  xli.  p.  437. 


Organic  Evolution. 


191 


affect  a  reduction  from  the  "  survival-mean  "  to  the  "  birth- 
mean."  This  was  referred  to  in  the  chapter  on  "Heredity 
and  the  Origin  of  Variations,"  but  may  be  again  indicated. 
Suppose  the  number  of  births  among  wild  ducks  be  repre- 
sented by  the  number  nine,  of  which  six  are  eliminated 
through  imperfections  in  the  organs  of  flight.  Let  us 
place  the  nine  in  order  of  merit  in  this  respect,  as  is  done 
in  the  table  on  p.  172.  The  average  wing-power  of  the 
nine  will  be  found  in  No.  5,  there  being  four  ducks  with 
superior  wing-power  (1 — 4),  and  four  with  inferior  wing- 
power  (6 — 9).  The  birth-mean  will  therefore  be  at  the 
level  of  No.  5,  as  indicated  to  the  left  of  the  table.  But  if 
six  ducks  with  the  poorest  wings  be  eliminated,  only  three 
survive.  The  average  wing-power  will  now  be  found  in 
No.  2,  one  duck  being  superior  and  one  inferior  to  it 
in  this  respect.  It  is  clear  that  this  survival-mean 
is  at  a  level  of  higher  excellence  than  the  birth-mean. 
Now,  when  the  ducks  are  placed  in  a  poultry-yard, 
selection  in  the  matter  of  flight  ceases,  and,  since  all 
nine  ducks  survive,  the  survival-mean  drops  to  the  birth- 
mean.  We  may  variously  estimate  this  retrogression  ;  but 
it  cannot  be  a  large  percentage — I  should  suppose,  in  the 
case  under  consideration,  one  or  two  per  cent,  at  most. 
But  Professor  Weismann  says,  "  A  continued  decline  from 
the  original  degree  of  development  must  inevitably  take 
place."  It  is  not  evident  why  such  decline  should  continue. 
If  variations  continue  in  the  same  proportion  as  before, 
the  birth-mean  will  be  preserved,  since  there  are  as  many 
positive  or  favourable  variations  above  the  mean  as  there 
are  negative  or  unfavourable  variations  below  the  mean. 
A  continuous  decline  must  result  from  a  preponderance  of 
negative  over  positive  variations,  and  for  this  some  other 
principle,  such  as  atavism,  or  reversion  to  ancestral 
characters,  must  be  called  in.  But  in  the  case  of  so  long- 
established  and  stable  an  organ  as  that  of  flight,  fixed 
and  rendered  constant  through  so  many  generations,  it  is 
hardly  probable  that  reversion  would  be  an  important 
factor.  Mr.  Galton  has  calculated  that  among  human- 


1 92  Animal  Life  and  Intelligence. 

folk  the  offspring  inherits  one-fourth  from  each  parent, 
one-sixteenth  from  each  grandparent,  leaving  one-fourth 
to  be  contributed  by  more  remote  ancestors.  There  is  no 
doubt,  however,  that  among  domesticated  animals  rever- 
sion occurs  to  characters  which  have  been  lost  for  many 
generations.  But  we  should  probably  have  to  go  a  very 
long  way  back  in  the  ancestry  of  wild  ducks  for  any  marked 
diminution  in  wing-power.  It  must  be  remembered  that, 
in  the  case  of  the  artificial  selection  of  domesticated 
animals,  man  has  been  working  against  and  not  with  the 
stream  of  ancestral  tendency.  Reversion  in  their  case  is 
towards  a  standard  which  was  long  maintained  and  had 
become  normal  before  man's  interference.  Reversion  in 
domesticated  ducks  should  therefore  be  towards  the  greater 
wing-power  of  their  normal  ancestry  before  domestication, 
not  in  the  direction  of  lessened  wing-power  and  diminished 
wing- structure.  The  whole  question  of  reversion  is  full  of 
interest,  and  needs  further  investigation. 

In  the  dwindling  of  disused  structures,  Mr.  Romanes 
has  suggested  "  failure  of  heredity  "  as  an  efficient  cause. 
I  find  it  difficult,  however,  to  distinguish  this  failure  of 
heredity  from  the  effects  of  disuse.  To  what  other  cause 
is  the  failure  of  heredity  due?  If  natural  selection  has 
intervened  to  hasten  this  failure,  this  can  only  be  because 
the  failure  is  advantageous,  since  it  permits  the  growth-force 
to  be  applied  more  advantageously  elsewhere.  And  this 
involves  a  different  principle.  Even  so  it  is  difficult  to 
exclude  the  possibility  (to  put  it  no  stronger)  that  the 
diversion  of  growth-force  from  a  less  useful  to  a  more 
useful  organ  is  in  part  due  to  the  use  of  the  one  and  the 
disuse  of  the  other.  •  But  of  disuse  Mr.  Romanes  says, 
"There  is  the  gravest  possible  doubt  lying  against  the. 
supposition  that  any  really  inherited  decrease  is  due  to 
the  inherited  effects  of  disuse."  We  may  fairly  ask  Mr. 
Romanes,  therefore,  to  explain  to  what  cause  the  failure  of 
heredity  is  due.  In  any  case,  Professor  Weismann  and 
his  school  are  not  likely  to  accept  this  failure  of  heredity 
as  an  efficient  factor  in  the  process.  Nor  is  Professor 


Organic  Evohition.  193 


Weismann  likely  to  fall  back  upon  any  innate  tendency  to 
degeneration.  Unless,  therefore,  some  cause  be  shown 
why  the  negative  variations  should  be  prepotent  over  the 
positive  variations,  we  must,  I  think,  allow  that  unaided 
panmixia  cannot  affect  any  great  amount  of  reduction. 

In  this  connection  we  may  notice  Professor  Weismann's 
newer  view  of  the  introduction  of  bodily  mortality.  He 
says,  "  The  problem  is  very  easily  solved  if  we  seek 
assistance  from  the  principle  of  panmixia.  As  soon  as 
natural  selection  ceases  to  operate  upon  any  character, 
structural  or  functional,  it  begins  to  disappear.  As  soon, 
therefore,  as  the  immortality  of  somatic  [body-]  cells  became 
useless,  they  would  begin  to  lose  this  attribute."  *  Even 
granting  that  panmixia  could  continuously  reduce  the  size 
of  ducks'  wings,  it  is  not  easy  to  see  how  it  could  get  rid  of 
immortality.  The  essence  of  the  idea  of  panmixia  is  that, 
when  the  natural  selection  which  has  raised  an  organ  to 
a  high  functional  level,  and  sustains  it  there,  ceases  or  is 
suspended,  the  organ  drops  back  from  its  high  level.  But 
on  Professor  Weismann's  hypothesis,  immortality  has 
neither  been  produced  nor  is  it  sustained  by  natural  selec- 
tion. How,  therefore,  the  cessation  of  selection  can  cause 
the  disappearance  of  immortality — a  character  with  which 
natural  selection  has  had  nothing  whatever  to  do — Pro- 
fessor Weismann  does  not  explain.  He  seems  to  be  using 
"panmixia"  in  the  same  vague  way  that,  in  his  previous 
explanation,  he  used  "  natural  selection." 

If  panmixia  alone  cannot,  to  any  very  large  extent, 
reduce  an  organ  no  longer  sustained  by  natural  selection, 
to  what  efficient  cause  are  we  to  look  ?  Mr.  Eomanes  has 
drawn  attention  to  the  reversal  of  selection  as  distinguished 
from  its  mere  cessation.  When  an  organ  is  being  improved 
or  sustained  by  selection,  elimination  weeds  out  all  those 
which  have  the  organ  in  an  ill-developed  form.  Under  a 
reversal  of  selection,  elimination  will  weed  out  all  those 
which  possess  the  organ  well  developed.  In  burrowing 
animals,  the  eyes  may  have  been  reduced  in  size,  or  even 

*  Weismann,  "  Essay  on  Heredity,"  p.  140. 

O 


194  Animal  Life  and  Intelligence. 

buried  beneath  the  skin,  through  a  reversal  of  selection. 
The  tuco-tuco  (Ctenomys),  a  burrowing  rodent  of  South 
America,  is  frequently  blind.  One  which  Darwin  kept 
alive  was  in  this  condition,  the  immediate  cause  being 
inflammation  of  the  nictitating  membrane.  "As  frequent 
inflammation  of  the  eyes,"  says  Darwin,  "must  be  in- 
jurious to  any  animal,  and  as  eyes  are  certainly  not 
necessary  to  animals  having  subterranean  habits,  a  reduc- 
tion in  their  size,  with  the  adhesion  of  the  eyelids  and 
growth  of  fur  over  them,  might  in  such  cases  be  an 
advantage ;  and,  if  so,  natural  selection  would  aid  the  effect 
of  disuse.*  Granting  that  the  inflammation  of  the  eyes  is 
a  sufficient  disadvantage  to  lead  to  elimination,  such  cases 
may  be  assigned  to  the  effects  of  a  reversal  of  selection. 

Perhaps  the  best  instances  of  the  reversal  of  selection 
are  to  be  found  in  the  insects  of  wind-swept  islands,  in 
which,  as  we  have  already  seen  (p.  81),  the  power  of  flight 
has  been  gradually  reduced  or  even  done  away  with. 
Such  instances  are,  however,  exceptional.  And  one  can 
hardly  suppose  that  such  reversal  of  selection  can  be  very 
far-reaching  in  its  effects,  at  least,  through  any  direct 
disadvantage  from  the  presence  of  the  organ.  One  can 
hardly  suppose  that  the  presence  of  an  eye  in  a  cave- 
dwelling  fisht  could  be  of  such  direct  disadvantage  as  to 
lead  to  the  elimination  of  those  members  which  still  possess 
this  structure. 

But  may  it  not  be  of  indirect  disadvantage  ?  May  not 
this  structure  be  absorbing  nutriment  which  would  be  more 
advantageously  utilized  elsewhere  ?  This  is  Darwin's 
principle  of  economy.  Granting  its  occurrence,  is  it  effec- 
tive ?  We  may  put  the  matter  in  this  way  :  The  Crustacea 
which  have  been  swept  into  a  dark  cave  may  be  divided 
into  three  classes  so  far  as  fortuitous  variations  of  eyes 

*  "  Origin  of  Species,"  p.  110. 

f  With  regard  to  bliud  cave-fish,  Professor  Ray  Lankester  has  suggested 
that  some  selection  has  been  effected.  Those  animals  whose  sight-sensitive- 
Bess  enabled  them  to  detect  a  glimmer  of  light  would  escape  to  the  exterior, 
leaving  those  with  congenitally  weak  sight  to  remain  and  procreate  in  the 
darkness  of  the  cave. 


Organic  Evolution.  195 

and  antennae  are  concerned.  First,  those  which  preserve 
eyes  and  antennas  in  the  original  absolute  and  relative 
proportion  and  value ;  secondly,  those  in  which,  while  the 
eyes  remain  the  same,  the  antennas  are  longer  and  more 
sensitive ;  thirdly,  those  in  which,  while  the  antennas  are 
longer  and  more  sensitive,  the  eyes  are  reduced  in  size  and 
elaboration.  According  to  the  principle  of  economy,  the 
third  class  have  sufficient  advantage  over  the  first  and 
second  to  enable  them  to  survive  and  escape  the  elimina- 
tion which  removes  those  with  fully  developed  eyes.  It 
may  be  so.  We  cannot  estimate  the  available  advantage 
with  sufficient  accuracy  to  deny  it.  But  we  may  fairly 
suppose  that,  in  general,  it  is  only  where  the  useless  organ 
in  question  is  of  relatively  large  size,  and  where  nutriment 
is  deficient,  that  economy  of  growth  is  an  important  factor. 

We  may  here  note  the  case  of  the  hermit  crab  as  one 
which  exemplifies  degeneration  through  the  reversal  of 
natural  selection.  This  animal,  as  is  well  known,  adopts 
an  empty  whelk-shell  or  other  gasteropod  shell  as  its  own. 
The  hinder  part  of  the  body  which  is  thus  thrust  into  the 
shell  loses  its  protective  armour,  and  is  quite  soft.  Pro- 
fessor WTeismann  seems  to  regard  this  loss  of  the  hardened 
cuticle  as  due  entirely  to  panmixia.  If  what  has  been 
urged  above  has  weight,  this  explanation  cannot  be  correct. 
No  amount  of  promiscuous  interbreeding  of  crabs  could 
reduce  the  cuticle  to  a  level  indefinitely  below  that  of  any 
of  the  interbreeding  individuals.  But  it  is  clear  that  an 
armour-sheathed  "tail"  would  be  exceedingly  ill  adapted 
to  thrusting  into  a  whelk-shell.  Hence  there  would,  by 
natural  selection,  be  an  adaptation  to  new  needs,  involving 
not  the  higher  development  of  cuticle,  but  the  reverse.  So 
far  as  the  cuticle  is  concerned,  it  is  a  case  of  reversed 
selection.  Whether  this  reversal  alone  will  adequately 
account  for  the  facts  is  another  matter. 

Mr.  Herbert  Spencer  has  made  a  number  of  observa- 
tions and  measurements  of  the  jaws  of  pet  dogs,  which  lead 
him  to  conclude  that  there  has  been  a  reduction  in  size 
and  muscular  power  due  to  disuse.  The  creatures  being 


196  Animal  Life  and  Intelligence. 

fed  on  sops,  have  no  need  to  use  to  any  large  extent  the 
jaw-muscles.  In  this  case,  he  argues,  the  principle  of 
economy  is  not  likely  to  be  operative,  since  the  pampered 
pet  habitually  overeats,  and  has  therefore  abundant  nutri- 
ment and  to  spare  to  keep  up  the  jaws.  It  is  possible, 
however,  that  artificial  selection  has  here  been  a  factor. 
There  may  have  been  a  competition  among  the  old  ladies 
who  keep  such  pets  to  secure  the  dear  little  dog  that  never 
bites,  while  the  nasty  little  wretch  that  does  occasionally 
use  his  jaws  for  illegitimate  purposes  may  have  been 
speedily  eliminated.  Pet  dogs  are,  moreover,  a  pampered, 
degenerate,  and  for  the  most  part  unhealthy  race,  often 
deteriorated  by  continued  in-breeding,  so  that  we  must  not 
build  too  much  on  Mr.  Spencer's  observations,  interesting 
as  they  undoubtedly  are. 

There  is  one  feature  about  the  reduction  of  organs 
which  must  not  be  lost  sight  of.  They  are  very  apt  to 
persist  for  a  long  time  as  remnants  or  vestiges.  The 
pineal  gland  is  the  vestigial  remnant  of  a  structure  con- 
nected with  the  primitive,  median,  or  pineal  eye.  The 
whalebone  whales  and  the  duck-bill  platypus  have  teeth 
which  never  cut  the  gum  and  are  of  no  functional  value. 
With  regard  to  these,  it  may  be  asked — If  disuse  leads  to 
the  reduction  of  unused  structures,  how  comes  it  that 
it  has  not  altogether  swept  away  these  quite  valueless 
structures  ?  In  considering  this  point,  we  must  notice  the 
unfortunate  and  misleading  way  in  which  disuse  is  spoken 
of  as  if  it  were  a  positive  determinant,  instead  of  the  mere 
absence  of  free  and  full  and  healthy  exercise.  Few  will 
question  the  fact  that  in  the  individual,  if  an  organ  is  to 
be  kept  up  to  its  full  standard  of  perfection,  it  must  be 
healthily  and  moderately  exercised ;  and  that,  if  not  so 
exercised,  it  will  not  only  cease  to  increase  in  size,  but  will 
tend  to  degenerate.  The  healthy,  functionally  valuable 
tissue  passes  into  the  condition  of  degenerate,  comparatively 
useless  tissue.  Now,  those  who  hold  that  the  inheritance 
of  functional  modifications  is  still  a  tenable  hypothesis, 
carry  on  into  the  history  of  the  race  that  which  they  find 


Organic  Evolution. 


197 


to  hold  good  in  the  history  of  the  individual.  They  believe 
that,  in  the  race,  the  continued  functional  activity  of  an 
organ  is  necessary  for  the  maintenance  of  the  integrity 
and  perfection  of  its  structure,  and  that,  if  not  so  exercised, 
the  organ  will  inevitably  tend  to  dwindle  to  embryonic 
proportions  and  to  degenerate.  The  healthy,  functionally 
valuable  tissue  passes  at  last  into  the  condition  of 
degenerate,  comparatively  useless  tissue.  The  force  of 
heredity  will  long  lead  to  the  production  in  the  embryo 
of  the  structure  which,  in  the  ancestral  days  of  healthy 
exercise,  was  to  be  of  service  to  the  organism.  At  this 
stage  of  life  the  conditions  have  not  changed.  The 
degeneration  sets  in  at  that  period  when  the  ancestral  use1 
is  persistently  denied.  There  is  no  reason  why  "  disuse  " 
should  in  all  cases  remove  all  remnants  of  a  structure ; 
but  if  the  presence  of  the  degenerate  tissue  is  a  source  of 
danger  to  the  organism  which  possesses  it,  that  organism 
will  be  eliminated,  and  those  (1)  which  possess  it  in  an 
inert,  harmless  form,  or  (2)  in  which  it  is  absent,  will 
survive.  Thus  natural  selection  (which  will  fall  under  Mr. 
Eomanes's  reversed  selection)  will  step  in — will  in  some 
cases  reduce  the  organ  to  a  harmless  and  degenerate 
rudiment,  and  in  others  remove  the  last  vestiges  of  the 
organ. 

On  the  whole,  even  taking  into  consideration  the  effects 
of  panmixia,  of  reversed  selection,  and  of  the  principle  of 
economy,  the  reduction  of  organs  is  difficult  to  explain, 
unless  we  call  into  play  "  disuse  "  as  a  co-operating  factor. 


Sexual  Selection,  or  Preferential  Mating. 

It  is  well  known  that,  in  addition  to  and  apart  from 
the  primary  sexual  differences  in  animals,  there  are  certain 
secondary  characters  by  which  the  males,  or  occasionally 
the  females,  are  conspicuous.  The  antlers  of  stags,  the 
tail  of  the  peacock,  the  splendid  plumes  of  the  male  bird  of 
paradise,  the  horns  or  pouches  of  lizards,  the  brilliant 
frilled  crest  of  the  newt,  the  gay  colours  of  male  stickle- 


198  Animal  Life  and  Intelligence. 

backs,  the  metallic  hues  of  male  butterflies,  and  the  large 
horns  or  antennae  of  other  insects, — these  and  many  other 
examples  which  will  at  once  occur  to  the  reader  are 
illustrations  of  the  fact. 

As  a  contribution  towards  the  explanation  of  this  order 
of  phenomena,  Darwin  brought  forward  his  hypothesis  of 
sexual  selection,  of  which  there  are  two  modes.  In  the 
first  place,  the  males  struggle  together  for  their  mates ;  in 
this  struggle  the  weakest  are  eliminated ;  those  possessed 
of  the  most  efficient  weapons  of  offence  and  defence  escape 
elimination.  In  the  second  place,  the  females  are  repre- 
sented as  exercising  individual  choice,  and  selecting  (in 
the  true  sense  of  the  word)  those  mates  whose  bright 
colours,  clear  voices,  or  general  strength  and  vigour  render 
them  most  pleasing  and  attractive.  For  this  mode  I  shall 
employ  the  term  "preferential  mating."  Combining  these 
two  in  his  summary,  Darwin  says,  "  It  has  been  shown 
that  the  largest  number  of  vigorous  offspring  will  be  reared 
from  the  pairing  of  the  strongest  and  best-formed  males, 
victorious  in  contests  over  other  males,  with  the  most 
vigorous  and  best-nourished  females,  which  are  the  first 
to  breed  in  the  spring.  If  such  females  select  the  more 
attractive  and,  at  the  same  time,  vigorous  males,  they  will 
rear  a  larger  number  of  offspring  than  the  retarded  females, 
which  must  pair  with  the  less  vigorous  and  less  attractive 
males.  So  it  will  be  if  the  more  vigorous  males  select 
the  more  attractive  and,  at  the  same  time,  healthy  and 
vigorous  females  ;  and  this  will  especially  hold  good  if  the 
male  defends  the  female,  and  aids  in  providing  food  for 
the  young.  The  advantage  thus  gained  by  the  more 
vigorous  pairs  in  rearing  a  larger  number  of  offspring  has 
apparently  sufficed  to  render  sexual  selection  efficient."* 

With  regard  to  the  first  of  the  two  modes,  little  need 
be  said.  There  can  be  no  question  that  there  are  both 
elimination  by  battle  and  elimination  by  competition  in 
the  struggle  for  mates.  It  is  well  known  that  the  emperor 
moth  discovers  his  mate  by  his  keen  sense  of  smell  residing 

*  Darwin,  "  Descent  of  Man,"  pt.  ii.  chap.  viii. 


Organic  Evolution.  199 


probably  in  the  large,  branching  antennae.  There  can 
be  little  doubt  that,  if  an  individual  is  deficient  in  this 
sense,  or  misinterprets  the  direction  in  which  the  virgin 
female  lies,  he  will  be  unsuccessful  in  the  competition  for 
mates ;  he  will  be  eliminated  from  procreation.  And  it  is 
a  familiar  observation  of  the  poultry-yard  that  the  law  of 
battle  soon  determines  which  among  the  cock  birds  shall 
procreate  their  kind.  The  law  of  battle  for  mates  is,  in- 
deed, an  established  fact  among  many  animals,  especially 
those  which  are  polygamous,  and  the  elimination  of  the 
unfit  in  this  respect  is  a  logical  necessity. 

It  is  when  we  come  to  the  second  of  the  two' modes, 
that  which  involves  selection  proper,  that  we  find  differences 
of  opinion  among  naturalists. 

Darwin,  as  we  have  seen,  suggested  that  those  secondary 
sexual  characters  which  can  be  of  no  value  in  aiding  their 
possessor  to  escape  elimination  by  combat  result  from  the 
preferential  choice  of  the  female,  the  female  herself  remain- 
ing comparatively  unaffected.  But  Mr.  Wallace  made  an 
exceedingly  valuable  suggestion  with  regard  to  these  com- 
paratively dull  colours  of  the  female.  He  pointed  out  that 
conspicuousness  (unless,  as  we  have  seen,  accompanied  by 
some  protective  character,  such  as  a  sting  or  a  bitter  taste) 
increased  the  risk  of  elimination  by  enemies.  Now,  the 
males,  since  they  are  generally  the  stronger,  more  active, 
and  more  pugnacious,  could  better  afford  to  run  this  risk 
than  their  mates.  They  could  to  some  extent  take  care 
of  themselves.  Moreover,  when  impregnation  was  once 
effected,  the  male's  business  in  procreation  was  over.  Not 
so  the  female ;  she  had  to  bear  the  young  or  to  lay  the 
eggs,  often  to  foster  or  nourish  her  offspring.  Not  only 
were  her  risks  greater,  but  they  extended  over  a  far  longer 
period  of  time.  Hence,  according  to  Mr.  Wallace,  the  dull 
tints  of  the  females,  as  compared  with  those  of  the  males, 
are  due  to  natural  selection  eliminating  the  conspicuous 
females  in  far  greater  proportion  than  the  gaudy  males. 

There  is  clearly  no  reason  why  this  view  should  not  be 
combined  with  Darwin's ;  preferential  mating  being  one 


2oc  Animal  Life  and  Intelligence. 

factor,  natural  elimination  being  another  factor;  both 
being  operative  at  the  same  time,  and  each  contributing  to 
that  marked  differentiation  of  male  and  female  which  we 
find  to  prevail  in  certain  classes  of  the  animal  kingdom. 

But  Mr.  Wallace  will  not  accept  this  compromise.  He 
rejects  preferential  mating  altogether,  or,  in  any  case, 
denies  that  through  its  agency  secondary  sexual  characters 
have  been  developed.  He  admits,  of  course,  the  striking 
and  beautiful  nature  of  some  of  these  characters ;  he 
admits  that  the  male  in  courtship  takes  elaborate  pains  to 
display  all  his  finery  before  his  would-be  mate ;  he  admits 
that  the  "  female  birds  may  be  charmed  or  excited  by  the 
fine  display  of  plumage  by  the  males ;  "  but  he  concludes 
that  "  there  is  no  proof  whatever  that  slight  differences  in 
that  display  have  any  effect  in  determining  their  choice  of 
a  partner."* 

How,  then,  does  Mr.  Wallace  himself  suppose  that 
these  secondary  sexual  characters  have  arisen  ?  His 
answer  is  that  "  ornament  is  the  natural  outcome  and 
direct  product  of  superabundant  health  and  vigour,"  and 
is  "due  to  the  general  laws  of  growth  and  development."! 
At  which  one  rubs  one's  eyes  and  looks  to  the  title-page  to 
see  that  Mr.  Wallace's  name  is  really  there,  and  not  that 
of  Professor  Mivart  or  the  Duke  of  Argyll.  For,  if  the 
plumage  of  the  argus  pheasant  and  the  bird  of  paradise 
is  due  to  the  general  laws  of  growth  and  development, 
why  not  the  whole  animal  ?  If  Darwin's  sexual  selection 
is  to  be  thus  superseded,  why  not  Messrs.  Darwin  and 
Wallace's  natural  selection  ? 

Must  we  not  confess  that  Mr.  Wallace,  for  whose  genius 
I  have  the  profoundest  admiration,  has  here  allowed  him- 
self to  confound  together  the  question  of  origin  and  the 
question  of  guidance  or  direction  ?  Natural  selection  by 
elimination  and  sexual  selection  through  preferential 

*  "  Darwinism,"  chap.  x. 

t  "Darwinism,"  p.  295.  Messrs.  Geddes  and  Thomson,  "  Tlie  Evolution 
of  Sex,"  p.  28,  also  contend  that  "combative  energy  and  sexual  beauty  rise 
part  passu  with  male  katabolism." 


Organic  Evolution.  201 

mating  are,  supposing  them  to  be  vera  causa,  guiding  or 
selecting  agencies.  Given  the  variations,  however  caused, 
these  agencies  will  deal  with  them,  eliminating  some, 
selecting  others,  with  the  ultimate  result  that  those 
specially  fitted  for  their  place  in  nature  will  survive. 
Neither  the  one  nor  the  other  deals  with  the  origin  of 
variations.  That  is  a  wholly  different  matter,  and  con- 
stitutes the  leading  biological  problem  of  our  day.  Mr. 
Wallace's  suggestion  is  one  which  concerns  the  origin  of 
variations,  and  as  such  is  worthy  of  careful  consideration. 
It  does  not  touch  the  question  of  their  guidance  into  certain 
channels  or  the  maintenance  of  specific  standards.  Con- 
cerning this  Mr.  Wallace  is  silent  or  confesses  ignorance. 
"Why,  in  allied  species,"  he  says,  "the  development  of 
accessory  plumes  has  taken  different  forms,  we  are  unable 
to  say,  except  that  it  may  be  due  to  that  individual 
variability  which  has  served  as  the  starting-point  for  so 
much  of  what  seems  to  us  strange  in  form  or  fantastic  in 
colour,  both  in  the  animal  and  vegetable  world."*  It  is 
clear,  however,  that  "individual  variability"  cannot  be 
regarded  as  a  vera  causa  of  the  maintenance  of  a  specific 
standard — a  standard  maintained  in  spite  of  variability. 

The  only  directive  agency  (apart  from  that  of  natural 
selection)  to  which  Mr.  Wallace  can  point  is  that  suggested 
by  Mr.  Alfred  Tylor,  in  an  interesting,  if  somewhat  fanciful, 
posthumous  work  on  "  Coloration  in  Animals  and  Plants," 
"  namely,  that  diversified  coloration  follows  the  chief  lines 
of  structure,  and  changes  at  points,  such  as  the  joints, 
where  function  changes."  But  even  if  we  admit  that 
coloration -bands  or  spots  originate  at  such  points  or 
along  such  lines — and  the  physiological  rationale  is  not 
altogether  obvious — even  if  we  admit  that  in  butterflies  the 
spots  and  bands  usually  have  reference  to  the  form  of  the 
wing  and  the  arrangement  of  the  nervures,  and  that  in 
highly  coloured  birds  the  crown  of  the  head,  the  throat, 
the  ear-coverts,  and  the  eyes  have  usually  distinct  tints, 
still  it  can  hardly  be  maintained  that  this  affords  us  any 

*  "  Darwinism,"  p.  293. 


2O2  Animal  Life  and  Intelligence. 

adequate  explanation  of  the  specific  colour-tints  of  the 
humming-birds,  or  the  pheasants,  or  the  Papilionidae 
among  butterflies.  If,  as  Mr.  Wallace  argues,  the  immense 
tufts  of  golden  plumage  in  the  bird  of  paradise  owe  their 
origin  to  the  fact  that  they  are  attached  just  above  the 
point  where  the  arteries  and  nerves  for  the  supply  of  the 
pectoral  muscles  leave  the  interior  of  the  body,  are  there 
no  other  birds  in  which  similar  arteries  and  nerves  are 
found  in  a  similar  position  ?  Why  have  these  no  similar 
tufts  ?  And  why,  in  the  birds  of  paradise  themselves,  does 
it  require  four  years  (for  it  takes  so  long  for  the  feathers 
of  the  male  to  come  to  maturity)  ere  these  nervous  and 
arterial  influences  take  effect  upon  the  plumage  ?  Finally, 
one  would  inquire  how  the  colour  is  determined  and  held 
constant  in  each  species.  The  difficulty  of  the  Tylor- 
Wallace  view,  even  as  a  matter  of  origin,  is  especially  great 
in  those  numerous  cases  in  which  the  colour  is  determined 
by  delicate  lines,  thin  plates,  or  thin  films  of  air  or  fluid.* 
Under  natural  selection,  as  we  have  seen,  the  develop- 
ment of  colour  is  fostered  under  certain  conditions.  The 
colour  is  either  protective,  rendering  the  organism  incon- 
spicuous amid  its  normal  surroundings,  or  it  is  of  warning 
value,  advertising  the  organism  as  inedible  or  dangerous, 
or,  in  the  form  of  recognition-marks,  it  is  of  service  in 
enabling  the  members  of  a  species  to  recognize  each  other. 
Now,  in  the  case  of  both  warning  colour  and  recognition- 
marks,  their  efficacy  depends  upon  the  perceptual  powers 
of  animals.  Unless  there  be  a  rapidly  acquired  and  close 
association  of  the  quality  we  call  nastiness  with  the  quality 
we  call  gaudiness  (though,  for  the  animal,  there  is  no  such 
isolation  of  these  qualities  as  is  implied  in  our  words  t), 
such  that  the  sight  of  the  gaudy  insect  suggests  that  it 
will  be  unpleasant  to  eat,  the  gaudiness  will  be  of  no  avail. 
And  if  there  is  any  truth  in  the  doctrine  of  mimicry,  the 
association  is  particular.  It  is  not  merely  that  bright 

*  Mr.  Poulton,  who  takes  a  similar  line  of  argument  in  his  "  Colours  of 
Animals,"  lays  special  stress  upon  the  production  of  white  (see  p,  326). 
t  See  Chapter  VIII. 


Organic  Evolution.  203 

colours  are  suggestive  of  a  nasty  taste.  The  insect-eating 
birds  associate  nastiness  especially  with  certain  markings 
and  coloration — "  the  tawny  Danais,  the  barred  Heliconias, 
the  blue-black  Euplceas,  and  the  fibrous  Acrceas;"  and 
this  is  proved  by  the  fact  that  sweet  insects  mimicking 
these  particular  forms  are  thereby  protected. 

So,  too,  with  recognition-marks.  If  the  bird  or  the 
mammal  have  not  sufficient  perceptive  powers  to  distinguish 
between  the  often  not  very  different  recognition-marks,  of 
what  service  can  they  be  ? 

Eecognition-marks  and  mimicry  seem,  therefore,  to  show 
that  in  the  former  case  many  animals,  and  in  the  latter 
the  insect-eating  birds,  mammals,  lizards,  and  other 
animals  concerned,  have  considerable  powers  of  perception 
and  association. 

Among  other  associations  are  those  which  are  at  the 
base  of  what  I  have  termed  preferential  mating.  We  must 
remember  how  deeply  ingrained  in  the  animal  nature  is 
the  mating  instinct.  We  may  find  it  difficult  to  distinguish 
closely  allied  species.  But  the  individuals  of  that  species 
are  led  to  mate  together  by  an  impelling  instinct  that  is  so 
well  known  as  to  elicit  no  surprise.  Instinct  though  it  be, 
however,  the  mating  individuals  must  recognize  each  other 
in  some  way.  The  impulse  that  draws  them  together  must 
act  through  perceptual  agency.  It  is  not  surprising,  there- 
fore, to  find,  when  we  come  to  the  higher  animals,  that, 
built  upon  this  basis,  there  are  well-marked  mating  pre- 
ferences. And  this,  as  we  have  before  pointed  out,  follow- 
ing Wallace,  is  an  efficient  factor  in  segregation.  Let  us, 
however,  hear  Mr.  Wallace  himself  in  the  matter. 

There  is,  he  says,*  "  a  very  powerful  cause  of  isolation 
in  the  mental  nature — the  likes  and  dislikes — of  animals  ; 
and  to  this  is  probably  due  the  fact  of  the  rarity  of  hybrids 
in  a  state  of  nature.  The  differently  coloured  herds  of 
cattle  in  the  Falkland  Islands,  each  of  which  keeps 
separate,  have  been  already  mentioned.  Similar  facts 
occur,  however,  among  our  domestic  animals,  and  are 

*  "  Darwinism,"  p.  172. 


204  Animal  Life  and  Intelligence. 

well  known  to  breeders.  Professor  Low,  one  of  the  greatest 
authorities  on  our  domesticated  animals,  says,  '  The  female 
of  the  dog,  when  not  under  restraint,  makes  selection  of 
her  mate,  the  mastiff  selecting  the  mastiff,  the  terrier  the 
terrier,  and  so  on.'  And  again,  '  The  merino  sheep  and 
the  heath  sheep  of  Scotland,  if  two  flocks  are  mixed  together, 
each  will  breed  with  its  own  variety.'  Mr.  Darwin  has 
collected  many  facts  illustrating  this  point.*  One  of  the 
chief  pigeon-fanciers  in  England  informed  him  that,  if 
free  to  choose,  each  breed  would  prefer  pairing  with  its 
own  kind.  Among  the  wild  horses  in  Paraguay  those  of 
the  same  colour  and  size  associate  together ;  while  in 
Circassia  there  are  three  races  of  horses  which  have 
received  special  names,  and  which,  when  living  a  free  life, 
almost  always  refuse  to  mingle  and  cross,  and  will  even 
attack  one  another.  In  one  of  the  Faroe  Islands,  not 
more  than  half  a  mile  in  diameter,  the  half-wild  native 
black  sheep  do  not  readily  mix  with  imported  white  sheep. 
In  the  Forest  of  Dean  and  in  the  New  Forest  the  dark 
and  pale  coloured  herds  of  fallow  deer  have  never  been 
known  to  mingle ;  and  even  the  curious  ancon  sheep,  of 
quite  modern  origin,  have  been  observed  to  keep  together, 
separating  themselves  from  the  rest  of  the  flock  when  put 
into  enclosures  with  other  sheep.  The  same  rule  applies 
to  birds,  for  Darwin  was  informed  by  the  Kev.  W.  D.  Fox 
that  his  flocks  of  white  and  Chinese  geese  kept  distinct. 
This  constant  preference  of  animals  for  their  like,  even 
in  the  case  of  slightly  different  varieties  of  the  same 
species,  is  evidently  a  fact  of  great  importance  in  con- 
sidering the  origin  of  species  by  natural  selection,  since  it 
shows  us  that,  so  soon  as  a  slight  differentiation  of  form  or 
colour  has  been  effected,  isolation  will  at  once  arise  by  the 
selective  association  of  the  animals  themselves." 

Mr.  Wallace  thus  allows,  nay,  he  lays  no  little  stress 
on,  preferential  mating,  and  his  name  is  associated  with 
the  hypothesis  of  recognition-marks.  But  he  denies  that 
preferential  mating,  acting  on  recognition-marks,  has  had 

*  See  "  Animals  and  Plants  under  Domestication,"  vol.  ii.  p.  80. 


Organic  Evolution.  205 

any  effect  in  furthering  a  differentiation  of  form  or  colour. 
He  admits  that  so  soon  as  a  slight  differentiation  of  form 
or  colour  has  been  effected,  segregation  will  arise  by  the 
selective  association  of  the  animals  themselves ;  but  he 
does  not  admit  that  such  selective  association  can  carry 
the  differentiation  further. 

Now,  it  is  clear  that  mating  preferences  must  be  either 
fixed  or  variable.  If  fixed,  how  can  differentiation  occur 
in  the  same  flock  or  herd?  And  how  can  selective  asso- 
ciation be  a  means  of  isolation  ?  Or,  granting  that  dif- 
ferentiation has  occurred,  if  the  mating  preferences  are 
then  stereotyped,  all  further  differentiation,  so  far  as  colour 
and  form  are  concerned,  will  be  rendered  impossible ;  for 
divergent  modifications,  not  meeting  the  stereotyped 
standard  of  taste,  will  for  that  reason  fail  to  be  perpetuated. 
We  must  admit,  then,  that  these  mating  preferences  are 
subject  to  variation.  And  now  we  come  to  the  central 
question  with  regard  to  sexual  selection  by  means  of 
preferential  mating.  What  guides  the  variation  along 
special  lines  leading  to  heightened  beauty  ?  This,  I  take 
it,  is  the  heart  and  centre  of  Mr.  Wallace's  criticism  of 
Darwin's  hypothesis.  Sexual  selection  of  preferential 
mating  involves  a  standard  of  taste  ;  that  standard  has 
advanced  from  what  we  consider  a  lower  to  what  we  con- 
sider a  higher  aesthetic  level,  not  along  one  line,  but  along 
many  lines.  What  has  guided  it  along  these  lines  ? 

Not  as  in  any  sense  affording  a  direct  answer  to  this 
question,  but  for  illustrative  purposes,  we  may  here  draw 
attention  to  what  seems  to  be  a  somewhat  parallel  case, 
namely,  the  development  of  flowers  through  insect  agency. 
In  his  "  Origin  of  Species,"  Darwin  contended  that  flowers 
had  been  rendered  conspicuous  and  beautiful  in  order  to 
attract  insects,  adding,  "  Hence  we  may  conclude  that,  if 
insects  had  not  been  developed  on  the  earth,  our  plants 
would  not  have  been  decked  with  beautiful  flowers,  but 
would  have  produced  only  such  poor  flowers  as  we  see  on 
our  fir,  oak,  nut,  and  ash  trees,  on  grasses,  docks,  and 
nettles,  which  are  all  fertilized  through  the  agency  of  the 


206  Animal  Life  and  Intelligence. 

wind."  "  The  argument  in  favour  of  this  view,"  says  Mr. 
Wallace,*  who  quotes  this  passage,  "is  now  much  stronger 
than  when  Mr.  Darwin  wrote ;  "  and  he  cites  with  approval 
the  following  passage  from  Mr.  Grant  Allen's  "  Colour- 
Sense  :  "  "  While  man  has  only  tilled  a  few  level  plains,  a 
few  great  river-valleys,  a  few  peninsular  mountain  slopes, 
leaving  the  vast  mass  of  earth  untouched  by  his  hand,  the 
insect  has  spread  himself  over  every  land  in  a  thousand 
shapes,  and  has  made  the  whole  flowering  creation  sub- 
servient to  his  daily  wants.  His  buttercup,  his  dandelion, 
and  his  meadowsweet  grow  thick  in  every  English  field. 
His  thyme  clothes  the  hillside  ;  his  heather  purples  the 
bleak  grey  moorland.  High  up  among  the  Alpine  heights 
his  gentian  spreads  its  lakes  of  blue  ;  amid  the  snows  of 
the  Himalayas  his  rhododendrons  gleam  with  crimson  light. 
Even  the  wayside  pond  yields  him  the  white  crowfoot  and 
the  arrowhead,  while  the  broad  expanses  of  Brazilian 
streams  are  beautified  by  his  gorgeous  water-lilies.  The 
insect  has  thus  turned  the  whole  surface  of  the  earth  into 
a  boundless  flower-garden,  which  supplies  him  from  year 
to  year  with  pollen  or  honey,  and  itself  in  turn  gains 
perpetuation  by  the  baits  that  it  offers  to  his  allurement."  t 
Mr.  Grant  Allen  is  perfectly  correct  in  stating  that  the 
insect  has  produced  all  this  beauty.  It  is  the  result  of 
insect  choice,  a  genuine  case  of  selection  as  contrasted  with 
elimination.  And  when  we  ask  in  this  case,  as  we  asked 
in  the  case  of  the  beautiful  colours  and  forms  of  animals, 
what  has  guided  their  evolution  along  lines  which  lead  to 
such  rare  beauty,  we  are  given  by  Mr.  Wallace  himself  the 
answer,  "  The  preferential  choice  of  insects."  If  these 
insects  have  been  able  to  produce  through  preferential 
selection  all  this  wealth  of  floral  beauty  (not,  indeed,  for  the 
sake  of  the  beauty,  but  incidentally  in  the  practical  business 
of  their  life),  there  would  seem  to  be  no  a  priori  reason  why 
the  same  class  and  birds  and  mammals  should  not  have 
been  able  to  produce,  through  preferential  selection,  all  the 
wealth  of  animal  beauty. 

*  "  Darwinism,"  p.  332.       f  "  The  Colour-Sense,"  by  Grant  Allen,  p.  95. 


Organic  Evolution.  207 

It  should  be  noted  that  the  answer  to  the  question  is  in 
each  case  a  manifestly  incomplete  one.  For  if  we  say  that 
these  forms  of  beauty,  floral  and  animal,  have  been  selected 
through  animal  preferences,  there  still  remains  behind  the 
question — How  and  why  have  the  preferences  taken  these 
(esthetic  lines  ?  To  which  I  do  not  see  my  way  to  a  satis- 
factory answer,  though  some  suggestions  in  the  matter  will 
be  made  in  a  future  chapter.*  At  present  all  we  can  say  is 
this — to  be  conspicuous  was  advantageous,  since  it  furthered 
the  mating  of  flowers  and  animals.  To  be  diversely  con- 
spicuous was  also  advantageous.  As  Mr.  Wallace  says, 
"It  is  probably  to  assist  the  insects  in  keeping  to  one 
flower  at  a  time,  which  is  of  vital  importance  to  the  per- 
petuation of  the  species,  that  the  flowers  which  bloom 
intermingled  at  the  same  season  are  usually  very  distinct, 
both  in  form  and  colour."  f  But  conspicuousness  is  not 
beauty.  And  the  question  still  remains — From  what  source 
comes  this  tendency  to  beauty  ? 

Leaving  this  question  on  one  side,  we  may  state  the 
argument  in  favour  of  sexual  selection  in  the  following 
form  :  The  generally  admitted  doctrine  of  mimicry  involves 
the  belief  that  birds  and  other  insect-eating  animals  have 
delicate  and  particular  perceptual  powers.  The  generally 
received  doctrine  of  the  origin  of  flowers  involves  the  belief 
that  their  diverse  forms  and  markings  result  from  the 
selective  choice  of  insects.  There  are  a  number  of  colour 
and  form  peculiarities  in  animals  that  cannot  be  explained 
by  natural  selection  through  elimination.  There  is  some 
evidence  in  favour  of  preferential  mating  or  selective  asso- 
ciation. It  is,  therefore,  permissible  to  hold,  as  a  pro- 
visional hypothesis,  that  just  as  the  diverse  forms  of  flowers 
result  from  the  preferential  choice  of  insects,  so  do  the 
diverse  secondary  sexual  characters  of  animals  result,  in 
part  at  least,  from  the  preferential  choice  of  animals  through 
selective  mating. 

If  this  be  admitted,  then  the  elaborate  display  of  their 
finery  by  male  birds,  which  Mr.  Wallace  does  admit,  may 

*  That  on  "  The  Emotions  of  Animals  "  (X.).         t  "  Darwinism,"  p.  318. 


208  Animal  Life  and  Intelligence. 

fairly  be  held  to  have  a  value  which  he  does  not  admit. 
For  if  preferential  mating  is  a  priori  probable,  such  display 
may  be  regarded  as  the  outcome  of  this  mode  of  selection. 
At  the  same  time,  it  may  be  freely  admitted  that  more 
observations  are  required.  In  a  recent  paper,  "  On  Sexual 
Selection  in  Spiders  of  the  Family  Attidee,"  *  by  George  \V. 
and  Elizabeth  G.  Peckham,  a  full,  not  to  say  elaborate, 
description  is  given  of  the  courtship,  as  they  regard  it,  of 
spiders.  The  "  love-dances  "  and  the  display  of  special 
adornments  are  described  in  detail.  And  the  observers, 
as  the  result,  be  it  remembered,  of  long  and  patient  investi- 
gation and  systematic  study,  come  to  the  conclusion  that 
female  spiders  exercise  selective  choice  in  their  mates. 
And  courtship  must  be  a  serious  matter  for  spiders,  for  if 
they  fail  to  please,  they  run  a  very  serious  risk  of  being 
eaten  by  the  object  of  their  attentions.  Some  years  ago  I 
watched,  on  the  Cape  Flats,  near  Capetown,  the  courtship 
of  a  large  spider  (I  do  not  know  the  species).  In  this  case 
the  antics  were  strange,  and,  to  me,  amusing;  but  they 
seemed  to  have  no  effect  on  the  female  spider,  who  merely 
watched  him.  Once  or  twice  she  darted  forward  towards 
him,  but  he,  not  liking,  perhaps,  the  gleam  in  her  eyes, 
retreated  hastily.  Eventually  she  seemed  to  chase  him  off 
the  field. 

We  must  remember  how  difficult  it  is  to  obtain  really 
satisfactory  evidence  of  mating  preferences  in  animals.  In 
most  cases  we  must  watch  the  animals  undisturbed,  and 
very  rarely  can  we  have  an  opportunity  of  determining 
whether  one  particular  female  selects  her  mate  out  of  her 
various  suitors.  We  watch  the  courtship  in  this,  that,  or 
the  other  case.  In  some  we  see  that  it  is  successful;  in 
others  that  it  is  unsuccessful.  How  can  we  be  sure  that 
in  the  one  case  it  was  through  fully  attaining,  in  the  other 
through  failing  to  reach,  the  standard  of  taste  ?  And  yet 
it  4s  evidence  of  this  sort  that  Mr.  Wallace  demands.  After 
noting  the  rejection  by  the  hen  of  male  birds  which  had 
lost  their  ornamental  plumage,  he  says,  "  Such  cases  do 

*  Natural  History  Society  of  Wisconsin,  vol.  i.  (1889). 


Organic  Evolution.  209 

not  support  the  idea  that  males  with  the  tail-feathers  a 
trifle  longer,  or  the  colours  a  trifle  brighter,  are  generally 
preferred,  and  that  those  which  are  only  a  little  inferior  are 
as'  generally  rejected, — and  this  is  what  is  absolutely  needed 
to  establish  the  theory  of  the  development  of  these  plumes 
by  means  of  the  choice  of  the  female."  *  If  Mr.  Wallace 
requires  direct  observational  evidence  of  this  kind,  I  do  not 
suppose  he  is  likely  to  get  any  large  body  of  it.  But  one 
might  fairly  ask  him  what  body  of  direct  observational 
evidence  he  has  of  natural  selection.  The  fact  is  that 
direct  observational  evidence  is,  from  the  nature  of  the 
processes  involved,  almost  impossible  to  produce  in  either 
case.  Natural  selection  is  an  explanation  of  organic 
phenomena  reached  by  a  process  of  logical  inference  and 
justified  by  its  results.  It  is  not  claimed  for  the  hypo- 
thesis of  selective  mating  that  it  has  a  higher  order  of 
validity. 


Use  and  Disuse. 

As  we  have  already  seen,  biologists  are  divided  into  two 
schools,  one  of  which  maintains  that  the  effects  of  use  and 
disuse  f  have  been  a  potent  factor  in  organic  evolution  ; 
the  other,  that  the  effects  of  use  and  disuse  are  restricted  to 
the  individual.  My  own  opinion  is  that  we  have  not  a 
sufficient  body  of  carefully  sifted  evidence  to  enable  us  to 
dogmatize  on  the  subject,  one  way  or  the  other.  But,  the 
position  of  strict  equilibrium  being  an  exceedingly  difficult 
and  som'e  would  have  us  believe  an  undesirable  attitude 
of  mind,  I  may  add  that  I  lean  to  the  view  that  use  and 
disuse,  if  persistent  and  long-continued,  take  effect,  not 
only  on  the  individual,  but  also  on  the  species. 

It  is  scarcely  necessary  to  give  examples  of  the  kind  of 
change  which,  according  to  the  Lamarckian  school,  are 
wrought  by  use  and  disuse.  Any  organ  persistently  used 
will  have  a  tendency,  on  this  view,  to  become  in  successive 

*  "  Darwinism,"  p.  286. 

t  On  the  negative  character  of  disuse,  see  p.  196. 

P 


2  TO  Animal  Life  and  Intelligence. 

generations  more  and  more  adapted  to  its  functional  work. 
To  give  but  one  example.  It  is  well  known  that  certain 
hoofed  creatures  are  divisible  into  two  groups — first,  those 
which,  like  the  horse,  have  in  each  limb  one  large  and 
strong!  digit  armed  with  a  solid  hoof ;  and,  secondly,  those 
which,  like  the  ox,  have  in  each  limb  two  large  digits,  so 
that  the  hoof  is  cloven  or  split.  It  is  also  well  known  that 
the  ancestral  forms  from  which  both  horse-group  and  ox- 
group  are  derived  were  possessed  of  five  digits  to  each 
limb.  Professor  Cop_g  regards  the  differentiation  of  these 
two  groups  as  the  result  of  the  different  modes  of  use 
necessitated  by  different  modes  of  life.  "  The  mechanical 
effect,"  he  says,  "  of  walking  in  the  mud  is  to  spread  the 
toes  equally  on  opposite  sides  of  the  middle  line.  This 
would  encourage  the  equal  development  of  the  digits  on 
each  side  of  the  middle  line,  as  in  the  cloven-footed  types. 
In  progression  on  hard  ground  the  longest  toe  (the  third) 
will  receive  the  greatest  amount  of  shock  from  contact  with 
the  earth."  *  Hence  the  solid-hoofed  types.  Here,  then, 
the  middle  digit  in  the  horse-group,  or  two  digits  in  the  ox- 
group,  having  the  main  burden  to  bear,  increase  through 
persistent  use,  while  the  other  digits  dwindle  through  dis- 
use, f 

On  the  other  hand,  one  who  holds  the  opposite  view  will 

*  Cope,  "  Origin  of  the  Fittest,"  p.  374. 

t  It  would  appear,  from  certain  passages  of  his  "  Darwinism,"  that  Mr. 
A.  K.  Wallace  (e.g.  p.  139,  note)  holds  or  held  similar  views.  "The 
genera  Aides  and  Colobus,"  he  says,  "  are  two  of  the  most  purely  arboreal 
types  of  monkeys,  and  it  is  not  difficult  to  conceive  that  the  constant  use  of 
the  elongated  fingers  for  climbing  from  tree  to  tree,  and  catching  on  o 
branches  while  making  great  leaps,  might  require  all  the  nervous  energy  and 
muscular  growth  to  be  directed  to  the  fingers,  the  small  thumb  remaining 
useless."  I  should  also  have  quoted  Mr.  Wallace's  account  of  the  twisting 
round  of  the  eyes  of  flat-fishes — where  he  says  that  the  constant  repetition 
of  the  effort  of  twisting  the  eye  towards  the  upper  side  of  the  head,  when 
the  bony  structure  is  still  soft  and  flexible,  causes  the  eye  gradually  to  move 
round  the  head  till  it  comes  to  the  upper  side — had  he  not  subsequently  dis- 
claimed this  explanation  (see  Nature,  vol.  xl.  p.  619).  It  is  possible  that  Mr. 
Wallace,  notwithstanding  the  words  "  constant  use "  in  the  passage  I  have 
quoted,  merely  intends  to  imply  that  the  elongated  fingers  are  of  advantage 
in  climbing,  and  are  thus  subject  to  natural  selection,  the  thumb  diminishing 
through  economy  of  growth. 


Organic  Evolution.  2 1 1 

say — I  do  not  believe  that  use  and  disuse  have  had  anything 
whatever  to  do  with  the  matter.  Fortuitous  variations  in 
these  digits  have  taken  place.  The  conditions  have  deter- 
mined which  variations  should  be  preserved.  In  the  horse, 
variations  in  the  direction  of  increase  of  functional  value 
of  the  mid  digit,  and  variations  in  the  simultaneous 
decrease  of  the  functional  value  of  the  lateral  digits,  have 
been  of  advantage,  and  have  therefore  survived  the  elimi- 
nating process  of  natural  selection. 

Now,  since  it  is  quite  clear,  in  this  and  numberless 
similar  cases,  that  we  can  explain  the  facts  either  way,  it 
is  obviously  not  worth  while  to  spend  much  time  or 
ingenuity  in  devising  such  explanations.  They  are  not 
likely  to  convince  any  one  worth  convincing.  What  we 
need  is  (1)  crucial  cases  which  can  only  be  explained  one 
way  or  the  other ;  or  (2)  direct  observation  or  experiment 
leading  to  the  establishment  of  one  hypothesis  or  the  other 
(or  both). 

1.  Crucial  cases  are  very  difficult  to  find.  We  cannot 
exclude  the  element  of  use  or  disuse,  for  on  both  hypotheses 
it  is  essential.  The  difference  is  that  one  school  says  the 
organ  is  developed  in  the  species  by  use  ;  the  other  school 
says  it  is  developed  for  use.  What  we  must  seek  is,  there- 
fore, the  necessary  exclusion  of  natural  selection ;  and  that 
is  not  easy  to  prove,  in  any  case,  to  a  Darwinian.  If  it  can 
be  shown  that  there  exist  structures  which  are  of  use,  but 
not  of  vital  importance  (that  is  to  say,  which  have  not 
what  I  called  above  the  available  advantage  necessary  to 
determine  the  question  of  elimination  or  not-elimination), 
then  we  are  perhaps  able  to  exclude  the  influence  of  natural 
selection.  I  think,  if  anywhere,  such  cases  are  to  be  found 
in  faculties  and  instincts  ;  *  and  as  such  they  must  be 
considered  in  a  later  chapter.  I  will,  however,  here  cite 
one  case  in  illustration  of  my  meaning. 


*  I  find,  on  rereading  one  of  his  articles,  that  I  have  here  unwittingly 
adopted  one  of  Mr.  Romanes's  arguments  (see  Nature,  vol.  xxxvi.  p.  406). 
The  instance  Mr.  Romanes  cites  is  the  curious  habit  of  dogs  turning  round 
before  they  lie  down. 


212  Animal  Life  and  Intelligence. 

We  have   seen  that  certain  insects  are  possessed  of 

warning   colours,  which  advertise  their   nastiness  to  the 

taste.     Birds  avoid  these  bright  but  unpleasant  insects, 

and  though  there  is  some  individual  learning,  there  seems 

to  be  an  instinctive  avoidance  of  these  unsavoury  morsels. 

There  is  hesitation  before  tasting;  and  one  or  two  trials 

are  sufficient  to  establish  the  association  of  gaudiness  and 

nastiness.     Moreover,  Mr.  Poulton  and  others  have  shown 

that,  under  the  stress  of  keen  hunger,  these  gaudy  insects 

may  be  eaten,  and  apparently  leave  no  ill  effects.     Birds 

certainly  instinctively  avoid  bees  and  wasps ;  and  yet  the 

sting  of  these  insects  can  seldom  be  fatal.     It  is,  therefore, 

improbable  that  nastiness  or  even  the  power  of  stinging 

can  have  been  an  eliminating  agency.     In  the  development 

of    the  instinctive   avoidance,   natural   selection   through 

elimination  seems  to  be  excluded,  and  the  inheritance  of 

individual  experience  is  thus  rendered  probable.     As  before 

pointed  out,  it  is  not  enough  to  say  that  a  nasty  taste  or  a 

sting  in  the  gullet  is  disadvantageous;  it  must  be  shown 

that  the  disadvantage  has  an  eliminating  value.     From 

my  experiments  (feeding  frogs  on  nasty  caterpillars,  and 

causing  bees  to  sting  chickens),  I  doubt  the  eliminating 

value  in  this  case.     Hence  elimination  by  natural  selection 

seems,  I  repeat,  to  be  excluded,  and  the  inheritance  of 

individual  experience  rendered  probable. 

Mr.  Herbert  Spencer  has  contended  that,  in  certain 
modifications,  natural  selection  is  excluded  on  the  grounds 
of  the  extreme  complexity  of  the  changes,  and  adduces  the 
case  of  the  Irish  "  elk  "  with  its  huge  antlers,  and  the  giraffe 
with  its  specially  modified  structure.  He  points  out  that 
in  either  case  the  conspicuous  modification — the  gigantic 
antlers  or  the  long  neck — involves  a  multitude  of  changes 
affecting  many  and  sometimes  distant  parts  of  the  body. 
Not  only  have  the  enormous  antlers  involved  changes  in 
the  skull,  the  bones  of  the  neck,  the  muscles,  blood-vessels, 
and  nerves  of  this  region,  but  changes  also  in  the  fore 
limbs ;  while  the  long  neck  of  the  giraffe  has  brought  with 
it  a  complete  change  of  gait,  the  co-ordinated  movements 


Organic  Evolution.  213 

of  the  hind  limbs  sharing  in  the  general  modification. 
Mr.  Spencer,  therefore,  argues  that  it  is  difficult  to  believe 
that  these  multitudinous  co-ordinated  modifications  are  the 
result  of  fortuitous  variations  seized  upon  by  natural  selec- 
tion. For  natural  selection  would  have  to  wait  for  the 
fortunate  coincidence  of  a  great  number  of  distinct  parts, 
all  happening  to  vary  just  in  the  particular  way  required. 
That  natural  selection  should  seize  upon  the  favourable 
modification  of  a  particular  part  is  comprehensible  enough ; 
that  two  organs  should  coincidently  vary  in  favourable 
directions  we  can  understand ;  that  half  a  dozen  parts 
should,  in  a  few  individuals  among  the  thousands  born,  by 
a  happy  coincidence,  vary  each  independently  in  the  right 
way  is  conceivable  ;  but  that  the  whole  organization  should 
be  remodelled  by  fortunately  coincident  and  fortuitously 
favourable  variations  is  not  readily  comprehensible.  It 
may  be  answered — Notwithstanding  all  this,  we  know  that 
such  happy  coincidences  have  occurred,  for  there  is  the 
resulting  giraffe.  The  question,  however,  is  not  whether 
these  modifications  have  occurred  or  not,  but  whether  they 
are  due  to  fortuitous  variation  alone,  or  have  been  guided 
by  functional  use.  The  argument  seems  to  me  to  have 
weight.* 

Still,  we  should  remember  that  among  neuter  ants — 
for  example,  in  the  Sauba  ant  of  South  America  (Oecodoma 
cephalotes} — there  are  certain  so-called  soldiers  with  rela- 
tively enormous  heads  and  mandibles.  The  possession  of 
these  parts  so  inordinately  developed  must  necessitate 
many  correlated  changes.  But  these  cannot  be  due  to 
inherited  use,  since  such  soldiers  are  sterile. 

Furthermore,  according  to  Professor  Weismann,  natural 
selection  is  really  working,  not  on  the  organism  at  large, 
but  on  the  germ-plasm  which  produces  it ;  and  it  is  con- 

*  Mr.  Darwin,  while  contending  that  the  modifications  need  not  all  have 
been  simultaneous,  says,  "  Although  natural  selection  would  thus  tend  to  give 
the  male  elk  its  present  structure,  yet  it  is  probable  that  the  inherited  effects 
of  use,  and  of  the  mutual  action  of  part  on  part,  have  been  equally  or  more 
important"  ("Animals  and  Plants  under  Domestication,"  vol.  ii.  p.  328). 


214  Animal  Life  and  Intelligence. 

ceivable  that  the  variation  of  one  or  more  of  the  few  cells 
in  early  embryonic  life  may  introduce  a  great  number  of 
variations  in  the  numerous  derivative  cells.  In  explana- 
tion of  my  meaning,  I  will  quote  a  paragraph  from  a  paper 
of  Mr.  E.  B.  Poulton's  on  "Theories  of  Heredity.*  "It 
appears,"  he  says,  "that,  in  some  animals,  the  great 
groups  of  cells  are  determined  by  the  first  division  [of  the 
ovum  in  the  process  of  cleavage  f];  in  others,  the  right 
and  left  sides,  or  front  and  hind  ends  of  the  body ;  while 
the  cells  giving  rise  to  the  chief  groups  on  each  side  would 
then  be  separated  at  some  later  division.  This  is  not 
theory,  but  fact ;  for  Eoux  has  recently  shown  that,  if  one 
of  the  products  of  the  first  division  of  the  egg  of  a  frog  be 
destroyed  with  a  hot  needle,  development  is  not  necessarily 
arrested,  but,  when  it  proceeds,  leads  to  the  formation  of 
an  embryo  from  which  either  the  right  or  the  left  side  is 
absent.  When  the  first  division  takes  place  in  another 
direction,  either  the  hind  or  the  front  half  was  absent  from 
the  embryo  which  was  afterwards  produced.  After  the 
next  division,  when  four  cells  were  present,  destruction  of 
one  produced  an  embryo  in  which  one-fourth  was  absent." 
Now,  it  is  conceivable  that  a  single  modification  or 
variation  of  the  primitive  germ  might  give  rise  to  many 
correlated  modifications  or  variations  of  the  numerous  cells 
into  which  it  develops ;  just  as  an  apparently  trivial 
incident  in  childhood  or  youth  may  modify  the  whole 
course  of  a  man's  subsequent  life.  It  is  difficult,  indeed, 
to  see  how  this  could  be  effected ;  to  understand  what  could 
be  the  nature  of  a  modification  of  the  germ  which  could 
lead  simultaneously  to  many  favourable  variations  of  bones, 
muscles,  blood-vessels,  and  nerves  in  different  parts  of  the 
body.  This,  however,  is  a  question  of  the  origin  of  varia- 
tions ;  and  it  is,  at  any  rate,  conceivable  that,  just  as  by 
the  extirpation  with  a  hot  needle  of  one  cell  of  the  cleaved 
frog's  ovum  all  the  anterior  part  of  the  body  should  be 
absent  in  development,  so  by  the  appropriate  modification 
of  this  one  cell,  or  the  germinal  matter  which  produced  it, 

*  Midland  Naturalist,  November,  1889.  t  See  ante,  p.  52. 


Organic  Evolution.  215 

all  the  anterior  part  of  the  body  should  be  appropriately 
modified. 

These  considerations,  perhaps,  somewhat  weaken  the 
force  of  Mr.  Spencer's  argument,  which  is  not  quite  so 
strong  now  as  it  was  when  the  "  Principles  of  Biology  " 
was  published. 

(2)  We  may  pass  now  to  the  evidence  afforded  by  direct 
observation  and  experiment.  There  is  little  enough  of  it. 
The  best  results  are,  perhaps,  those  which  have  been 
incidentally  reached  in  the  poultry-yard  and  on  the  farm 
in  the  breeding  of  domesticated  animals.  We  have  seen 
that,  under  these  circumstances,  certain  parts  or  organs 
have  very  markedly  diminished  in  size  and  efficiency ; 
others  have  as  markedly  increased.  Of  the  former,  or 
decrease  in  size  and  efficiency,1  the  imbecile  ducks  with 
greatly  diminished  brains  have  been  already  mentioned. 
Mr.  Herbert  Spencer  draws  attention  *  to  the  diminished 
efficiency  in  ear-muscles,  giving  rise  to  the  drooping  ears 
of  many  domesticated  animals.  "  Cats  in  China,  horses  in 
parts  of  Eussia,  sheep  in  Italy  and  elsewhere,  the  guinea- 
pig  formerly  in  Germany,  goats  and  cattle  in  India,  rabbits, 
'  pigs,  and  dogs  in  all  long-civilized  countries,  have  dependent 
ears."  f  Since  many  of  these  animals  are  habitually  well 
fed,  the  principle  of  economy  of  growth  seems  excluded. 
Indeed,  the  ears  are  often  unusually  large;  it  is  only 
their  motor  muscles  that  have  dwindled  either  relatively 
or  absolutely.  If  what  has  been  urged  above  be  valid, 
panmixia  cannot  have  been  operative  ;  since  panmixia  per 
se  only  brings  about  regression  to  mediocrity.  If  the  effects 
in  these  two  cases,  ducks'  brains  and  dogs'  ears,  be  not  due 
to  disuse,  we  know  not  at  present  to  what  they  are  due. 
In  the  correlative  case  of  increase  by  use,  we  find  it  exceed- 
ingly difficult  to  exclude  the  disturbing  effects  of  artificial 
selection.  The  large  and  distended  udders  of  cows,  the 
enhanced  egg-laying  powers  of  hens,  the  fleetness  or 
strength  of  different  breeds  of  horses, — all  of  these  have  been 

*  Nature,  vol.  xli.  p.  511. 

f  "Animals  and  Plants  under  Domestication,"  vol.  ii.  p.  291. 


216  Animal  Life  and  Intelligence. 

subjects  of  long-continued,  assiduous,  and  careful  selection. 
One  cannot  be  sure  whether  use  has  co-operated  or  not. 

Sufficient  has  now,  I  think,  been  said  to  show  the 
difficulty  of  deciding  this  question,  the  need  of  further 
observation  and  discussion,  and  the  necessity  for  a  recep- 
tive rather  than  a  dogmatic  attitude  ;  and  sufficient,  also, 
to  indicate  my  reasons  for  leaning  to  the  view  that  use  and 
disuse,  long-continued  and  persistent,  may  be  a  factor  in 
organic  evolution. 


The  Nature  of  Variations. 

The  diversity  of  the*  variations  which  are  possible,  and 
which  actually  occur  in  animal  life,  is  so  great  that  it  is 
not  easy  to  sum  up  in  a  short  space  the  nature  of  variations. 
Without  attempting  anything  like  an  exhaustive  classifica- 
tion, we  may  divide  variations  into  three  classes. 

1.  Superficial  variations  in  colour,  form,  etc.,  not  neces- 
sarily in  any  way  correlated  with 

2.  Organic    variations    in   the    size,    complexity,    and 
efficiency  of  the  organs  of  the  body  ; 

3.  Reproductive  and  developmental  variations. 

Any  of  these  variations,  if  sufficient  in  amount  and 
value  to  determine  the  question  of  elimination  or  not-elimi- 
nation,  selection  or  not-selection,  may  be  seized  upon  by 
natural  selection. 

Our  domesticated  animals  exemplify  very  fully  the 
superficial  variations  which,  through  man's  selection,  have 
in  many  cases  been  segregated  and  to  some  extent  stereo- 
typed. It  is  unnecessary  to  do  more  than  allude  to  the 
variations  in  form  and  coloration  of  dogs,  cattle,  fowls,  and 
pigeons.  These  variations  are  not  nec^ssarih^in&Tiy  way 
correlated  witn  any  deeper  organic  variations.  [TEeylire, 
h^eve77in~ma^^cas^8^s^cp£related.  For  exampLeTlihe 
form  of  the  pouter  pigeonis~a>rrelated  with  the  increased 
size  of  the  crop,  the  length  of  the  beak  carries  with  it  a 
modification  of  the  tongue,  the  widely  expanded  tail  of  the 
fantail  carries  with  it  an  increase  in  the  size  and  number 


Organic  Evolution.  217 

of  the  caudal  vertebrae.  And  here  we  might  take  the  whole 
series  of  secondary  sexual  characters.  These  and  their 
like  may  be  said  to  be  direct  correlations.  But  there  are 
also  correlations  which  are  seemingly  indirect,  their  con- 
nection being  apparently  remote.  That  in  pigeons  the 
size  of  the  feet  should  vary  with  the  size  of  the  beak  ;  that 
the  length  of  the  wing  and  tail  feathers  should  be  corre- 
lated ;  that  the  nakedness  of  the  young  should  vary  with 
the  future  colour  of  the  plumage  ;  that  white  dogs  should 
be  subject  to  distemper,  and  white  fowls  to  the  "  gapes  ;  " 
that  white  cats  with  blue  eyes  should  be  nearly  always 
deaf  ;  —  in  these  cases  the  correlation  is  indirect.  But  from 
the  existence  of  correlation,  whether  direct  or  indirect,  it 
follows  that  variations  seldom  come  singly.  The  organism 
is  so  completely  a  unity  that  the  variation  of  one  part,  even  in 
superficial  matters,  affects  directly  or  indirectly  other  parts. 
In  the  freedom  of  nature  such  superficial  variations  are 
not  so  obvious.  But  among  the  invertebrates  they  are  not 
inconsiderable.  The  case  of  land-snails,  already  quoted, 
may  again  be  cited.  Taking  variations  in  banding  alone, 
Mr.  Cockerell  knows  of  252  varieties  of  Helix  nemoralis 
and  128  of  H.  hortensis.  Still,  among  the  wild  relatives  of 
our  domestic  breeds  of  animals  and  birds  the  superficial 
variations  are  decidedly  less  marked.  And  this  is  partly 
due  to  the  fact  that  they  are  in  a  state  of  far  more  stable 
equilibrium  than  our  domestic  products,  and  partly  to  the 
constant  elimination  of  all  variants  which  are  thereby 
placed  at  a  serious  or  vital  disadvantage.  .  White  rats, 
mice,  or  small  birds,  in  temperate  regions,  would  soon  be 
seized  upon  by  hawks  and  other  enemies.  If  the  eggs  and 
young  of  the  Kentish  plover,  shown  in  our  frontispiece, 
were  white  or  yellowish,  like  the  eggs  and  young  of  our 
fowls,  they  would  soon  be  snapped  up.  The  varied  protec- 
tive resemblances,  general  and  special,  have  been  brought 
about  by  the  superficial  variations  of  organisms,  and  the 
elimination  of  those  which,  from  non-variation  or  wrong 
variation,  remained  conspicuous.  We  need  only  further 
notice  one  thing  here,  namely,  that,  in  the  case  of  special 


218  Animal  Life  and  Intelligence. 

resemblance  to  an  inorganic  object  or  to  another  organism, 
the  variations  of  the  several  parts  must  be  very  closely, 
and  sometimes  completely,  correlated.  The  correlations, 
however,  need  not,  perhaps,  have  been  simultaneous — the 
resemblance  having  been  gradually  perfected  by  the  filling 
in  of  additional  touches,  first  one  here,  then  another  there, 
and  so  on. 

Concerning  "  organic  variations,"  little  need  be  said. 
It  is  clear  that  an  organ  or  limb  may  vary  in  size,  such 
variation  carrying  with  it  a  correlative  variation  in  power ; 
or  it  may  vary  in  complexity — the  teeth  of  the  horse  tribe, 
for  example,  having  increased  in  complexity,  while  their 
limbs  have  been  rendered  less  complex ;  or  it  may  vary 
in  efficiency  through  the  more  perfect  correlation  and  co- 
ordination of  its  parts. 

The  evidence  of  such  variations  from  actual  observation 
is  far  less  in  amount  than  that  of  superficial  variations. 
And  this  is  not  to  be  wondered  at,  since  in  many  cases 
it  can  only  be  obtained  by  careful  anatomical  investigation. 
Nevertheless,  anatomists,  both  human  and  comparative, 
are  agreed  that  such  variations  do  occur.  And  no  one  can 
examine  such  a  collection  as  that  of  the  Koyal  College  of 
Surgeons  without  acknowledging  the  fact. 

Thirdly,  "  reproductive  and  developmental  variations  " 
are  of  very  great  importance.  The  following  are  among 
the  more  important  modifications  which  may  occur  in  the 
animal  kingdom. 

1.  Variations  in  the  mode  of  reproduction,  sexual  or 
asexual. 

2.  Variations  in  the  mode  of  fertilization. 

3.  Variations  in  the  number  of  fertilized  ova  produced. 

4.  Variations  in  the  amount  of  food-yolk  and  in  the 
way  in  which  it  is  supplied. 

5.  Variations  in  the  time  occupied  in  development. 

6.  Variations  in  the  time  at  which  reproduction  com- 
mences. 

7.  Variations  in  the  duration  and  amount  of  parental 
protection  and  fosterage. 


Organic  Evolution.  219 

8.  Variations  in  the  period  at  which  secondary  sexual 
characters  and  the  maximum  efficiency  of  the  several 
organs  is  reached. 

It  is  impossible  here  to  discuss  these  modes  of  variation 
seriatim.  I  shall  therefore  content  myself  with  but  a  few 
remarks  on  the  importance  of  protection  and  fosterage.  It 
is  not  too  much  to  say  that,  without  fosterage  and  protec- 
tion, the  higher  forms  of  evolution  would  be  impossible.  If 
you  are  to  have  a  highly  evolved  form,  you  must  allow 
time  for  its  evolution  from  the  egg;  and  that  develop- 
ment may  go  on  without  let  or  hindrance,  you  must  supply 
the  organism  with  food  and  lighten  the  labour  of  self- 
defence.  Most  of  the  higher  organisms  are  slow  in  coming 
to  maturity,  passing  through  stages  when  they  are  helpless 
and,  if  left  to  themselves,  would  inevitably  fall  a  prey  to 
enemies. 

In  those  animals  in  which  the  system  of  fosterage  and 
protection  has  not  been  developed  a  great  number  of 
fertilized  ova  are  produced,  only  a  few  of  which  come  to 
maturity.  It  might  be  suggested  that  this  is  surely  an 
advantage,  since  the  greater  the  number  produced  the 
greater  the  chances  of  favourable  variations  taking  place. 
But  it  has  before  been  pointed  out  that  these  great  numbers 
are  decimated,  and  more  than  decimated,  not  by  elimina- 
tion, but  by  indiscriminate  destruction ;  embryos,  good, 
bad,  and  indifferent,  being  alike  gobbled  up  by  those  who 
had  learnt  the  secret  of  fostering  their  young.  The 
alternative  has  been  between  producing  great  numbers  *  of 
embryos  which  soon  fend  for  themselves,  and  a  few  young 
who  are  adequately  provided  for  during  development.  And 
the  latter  have  proved  the  winners  in  life's  race.  If  we 
compare  two  flat-fishes  belonging  to  very  different  groups, 
the  contrast  here  indicated  will  be  readily  seen.  The 
skate  is  a  member  of  the  shark  tribe,  flattened  sym- 

*  In  the  third  chapter  we  saw  that  in  such  cases  not  only  are  there  an 
enormous  number  of  ova  produced,  but  that  (e.g.  in  aurelia  and  the  liver- 
fluke)  each  ovum  produces,  through  the  intervention  of  asexual  multiplica- 
tion, many  individuals. 


220  Animal  Life  and  Intelligence. 

metrically  from  above  downwards.  It  lays,  perhaps,  eighty 
to  a  hundred  eggs.  Each  of  these  is  large,  and  has  a 
rich  supply  of  nutritive  food-yolk.  Each  is  also  protected 
by  a  horny  case  with  pointed  corners — the  so-called  sea- 
purse  of  seaside  visitors.  These  are  committed  by  the 
skate  to  the  deep,  and  are  not  further  cared  for.  But  the 
abundant  supply  of  food-yolk  gives  the  little  skate  which 
emerges  a  good  start  in  life.  On  the  other  hand,  the 
turbot,  one  of  the  bony  fishes,  flattened  from  side  to  side 
with  an  asymmetrical  head,  lays  several  millions  of  eggs, 
which  float  freely  in  the  open  sea.  These  are  minute  and 
glassy,  and  not  more  than  one-thirtieth  of  an  inch  in 
diameter.  When  the  fishes  are  hatched,  they  are  not 
more  than  about  one-fifth  of  an  inch  in  length.  The 
slender  stock  of  food-yolk  is  soon  used  up,  and  henceforth 
the  little  turbot  (at  present  more  like  a  stump-nosed  eel 
than  a  turbot)  has  to  get  its  own  living.  Hundreds  of 
thousands  of  them  are  eaten  by  other  fishes. 

Or,  if  we  compare  such  different  vertebrates  as  a  frog,  a 
sparrow,  and  a  mouse,  we  find  that  the  frog  produces  a 
considerable  number  of  fertilized  ova,  though  few  in  com- 
parison with  the  turbot,  each  provided  with  a  small  store 
of  food-yolk.  The  tiny  tadpoles  very  soon  have  to  obtain 
their  own  food  and  run  all  the  risks  of  destruction.  Few 
survive.  The  sparrow  lays  a  few  eggs;  but  each  is 
supplied  with  a  large  store  of  food-yolk,  sufficient  to  meet 
its  developmental  needs  until,  under  the  fostering  influence 
of  maternal  warmth,  it  is  hatched.  Even  on  emerging 
from  the  eggs,  the  callow  fledglings  enjoy  for  a  while 
parental  protection  and  fosterage,  and,  when  sent  forth 
into  the  world,  are  very  fairly  equipped  for  life's  struggle. 
The  mouse  produces  minute  eggs  with  little  or  no  food- 
yolk  ;  but  they  undergo  development  within  the  womb  of 
the  mother,  and  are  supplied  with  nutrient  fluids  elaborated 
within  the  maternal  organism.  Even  when  born,  they  are 
cherished  for  a  while  and  supplied  with  food-milk  by  the 
mother. 

The  higher  stages  of  this  process  involve  a  mental 


Organic  Evolution.  221 

element,  and  are  developed  under  the  auspices  of  in- 
telligence or  instinct.  But  the  lower  stages,  the  supply  of 
food-yolk  and  intra-uterine  protection,  are  purely  organic. 
A  hen  cannot  by  instinctive  or  intelligent  forethought 
increase  the  amount  of  food-yolk  stored  up  in  the  ovum, 
any  more  than  the  lily,  which,  by  an  analogous  process, 
stores  up  in  its  bulb  during  one  year  material  for  the  best 
part  of  next  year's  growth,  can  increase  this  store  by  a 
mental  process. 

It  cannot  therefore  be  questioned  that  variations  in  the 
amount  of  capital  with  which  an  embryo  is  provided  in 
generation  would  very  materially  affect  its  chances  of 
escaping  elimination  by  physical  circumstances,  by  enemies, 
and  by  competition. 

Nor  can  it  be  questioned  that  variations  in  the  time 
occupied  in  reaching  maturity  would,  other  things  equal, 
not  a  little  affect  the  chances  of  success  of  an  organism  in 
the  competition  of  life.  Hence  we  have  the  phenomena 
of  what  may  be  termed  acceleration  and  retardation  in 
development.  These  terms  have,  however,  been  used  by 
American  zoologists,  notably  Professors  Hyatt  and  Cope, 
in  a  somewhat  different  and  wider  sense ;  for  they  include 
not  merely  time-changes,  but  also  the  loss  of  old  characters 
or  the  acquisition  of  new  characters.  "It  is  evident," 
says  Professor  Cope,  "  that  the  animal  which  adds  some- 
thing to  its  structure  which  its  parents  did  not  possess 
has  grown  more  than  they;  while  that  which  does  not 
attain  to  all  the  characteristics  of  its  ancestors  has  grown 
less  than  they."  "  If  the  embryonic  form  be  the  parent,  the 
advanced  descendant  is  produced  by  an  increased  rate  of 
growth,  which  phenomenon  is  called  '  acceleration ; '  but  if 
the  embryonic  type  be  the  offspring,  then  its  failure  to 
attain  the  condition  of  the  parent  is  due  to  the  supervention 
of  a  slower  rate  of  growth ;  to  this  phenomenon  the  term 
'retardation'  is  applied."  "I  believe  that  this  is  the 
simplest  mode  of  stating  and  explaining  the  law  of  varia- 
tion :  that  some  forms  acquire  something  which  their 
parents  did  not  possess;  and  that  those  which  acquire 


222  Animal  Life  and  Intelligence. 

something  additional  have  to  pass  through  more  numerous 
stages  than  their  ancestors ;  and  those  which  lose  some- 
thing pass  through  fewer  stages  than  their  ancestors  ;  and 
these  processes  are  expressed  by  the  terms  '  acceleration ' 
and  '  retardation.'  "  * 

It  is  clear,  however,  that  we  have  here  something  more 
than  acceleration  and  retardation  of  development  in  the 
ordinary  sense  of  these  words.  It  would  be,  therefore,  more 
convenient  to  use  the  term  "  acceleration  "  for  the  con- 
densation of  the  same  series  of  developmental  changes  into  a 
shorter  period  of  time ;  "  retardation  "  for  the  lengthening  of 
the  period  in  which  the  same  series  of  changes  are  effected ; 
and  "  arrested  development "  for  those  cases  in  which  the 
young  are  born  in  an  immature  or  embryonic  condition. 
"Whether  there  is  any  distinct  tendency,  worthy  of  formu- 
lation as  a  law,  for  organisms  to  acquire,  as  a  result  of 
protracted  embryonic  development,  definite  characteristics 
which  their  ancestors  did  not  possess,  I  think  very  question- 
able. If  so,  this  will  fall  under  the  head  of  the  origin  of 
variations. 

That  acceleration,  in  the  sense  in  which  I  have  used 
the  term,  does  occur  as  a  variation  is  well  known.  "  With 
our  highly  improved  breeds  of  all  kinds,"  says  Darwin,t 
"  the  periods  of  maturity  and  reproduction  have  advanced 
with  respect  to  the  age  of  the  animal ;  and  in  correspondence 
with  this,  the  teeth  are  now  developed  earlier  than  formerly, 
so  that,  to  the  surprise  of  agriculturalists,  the  ancient  rules 
for  judging  of  the  age  of  an  animal  by  the  state  of  its  teeth 
are  no  longer  trustworthy."  "  Disease  is  apt  to  come  on 
earlier  in  the  child  than  in  the  parent ;  the  exceptions  in 
the  other  direction  being  very  much  rarer."  }  Professor 
Weismann  contends  that  the  time  of  reproduction  has  been 
accelerated  through  natural  selection,  since  the  shorter  the 
time  before  reproduction,  the  less  the  number  of  possible 
accidents.  We  may,  perhaps,  see  in  the  curious  cases  of 

*  Cope,  "  Origin  of  the  Fittest,  "  pp.  226,  125,  and  297. 

f  "  Animals  and  Plants  under  Domestication,"  vol.  ii.  p.  313. 

$  Ibid.  p.  56. 


Organic  Evohition.  223 

reproduction  during  an  otherwise  immature  condition, 
extreme  instances  of  acceleration.  The  axolotl  habitually 
reproduces  in  the  gilled,  or  immature  condition.  Some 
species  of  insects  reproduce  before  they  complete  their 
metamorphoses.  And  the  females  of  certain  beetles  (Phen- 
godini)  are  described  by  Professor  Eiley  as  larviform.* 

Precocity  is  variation  in  the  direction  of  acceleration, 
and  that  condensed  development  which  is  familiar  in  the 
embryos  of  so  many  of  the  higher  animals  may  be  regarded 
as  the  result  of  variations  constantly  tending  in  the  same 
direction.  That  there  are  fewer  examples  of  retardation 
is  probably  due  to  the  fact  that  nature  has  constantly 
favoured  those  that  can  do  the  same  work  equally  well  in 
a  shorter  time  than  their  neighbours.  But  there  can  be 
no  doubt  that,  accompanying  that  fosterage  and  protection 
which  is  of  such  marked  import  in  the  higher  animals, 
there  is  also  much  retardation.  And  as  bearing  upon  the 
supposed  law  of  variation  as  formulated  by  Messrs.  Hyatt 
and  Cope,  it  should  be  noted  that  this  retardation  or 
decreased  rate  of  growth  leads  to  the  production  of  the 
more  advanced  descendant. 


The  Inheritance  of  Variations. 

Given  the  occurrence  of  variations  in  certain  individuals 
of  a  species,  we  have  the  alternative  logical  possibilities 
of  their  being  inherited  or  their  not  being  inherited.  The 
latter  alternative  seems  at  first  sight  to  be  in  contradiction 
to  the  law  of  persistence.  Sir  Henry  Holland,  seeing  this, 
remarked  that  the  real  subject  of  surprise  is,  not  that  a 
character  should  be  inherited,  but  that  any  should  ever 
fail  to  be  inherited,  t  Intercrossing  may  diminish  a 
character,  and  sooner  or  later  practically  obliterate  it : 
annihilate  it  at  once  and  in  the  first  generation  it  cannot. 
This  logical  view,  however,  ceases  to  be  binding  if  we  admit, 

*  Nature,  vol.  xxxvi.  p.  592. 

t  Quoted  from  "  Medical  Notes  and  Reflections,"  1855,  p.  267,  by  Darwiu, 
"  Animals  arid  Plants  under  Domestication,"  vol.  i.  p.  446. 


224  Animal  Life  and  Intelligence. 

with  Professor  Weismann,  that  variations  may  be  produced 
in  the  body  without  in  any  way  affecting  the  germ.  It  is 
also  vitally  affected  if  we  believe  that  the  hen  does  not 
produce  the  egg,  though  she  may,  perhaps,  modify  the  eggs 
inside  her ;  for  the  modification  of  the  hen  (i.e.  the  variety 
in  question)  may  not  be  of  the  right  nature  or  of  sufficient 
strength  to  impress  itself  upon  the  germinal  matter  of  the 
egg.  We  may  at  once  admit,  then,  that  acquired  varia- 
tions need  not  be  inherited. 

Passing^P  innate  variations — variations,  that  is  to  say, 
which  are  the  outcome  of  normal  development  from  the 
fertilized  ovum — must  they  be  inherited,  at  any  rate,  in 
some  degree  ?  It  seems  to  me  that  they  must,  on  the 
hypothesis  that  sexual  generation  involves  simply  the 
blending  or  commingling  of  the  characters  handed  on  in 
the  ovum  or  the  sperm.  The  only  cases  where  this  would 
apparently  fail  to  hold  good  would  be  where  the  ovum 
and  the  sperm  handed  on  exactly  opposite  tendencies — 
a  variation  in  excess  contributed  by  the  male  precisely 
counterbalancing  a  variation  in  the  opposite  direction  con- 
tributed by  the  female  parent.  Even  here  the  tendency  is 
inherited,  though  it  is  counterbalanced.  On  the  hypothesis 
of  "organic  combination"  before  alluded  to  (p.  150),  varia- 
tions might,  however,  in  the  union  of  ovum  and  sperm, 
be  not  only  neutralized,  but  augmented.  If  the  variation 
be,  so  to  speak,  a  definite  organic  compound  resulting  from 
a  fortunate  combination  of  characters  in  ovum  and  sperm, 
it  might  either  fail  altogether,  or  be  repeated  in  an  en- 
feebled form,  or  augmented  in  the  offspring,  according  as 
the  new  conditions  of  combination  were  unfavourable  or 
favourable. 

Whether  innate  variations  ever  actually  fail  to  be 
inherited,  even  in  an  enfeebled  form,  it  is  very  difficult  to 
say ;  for  if  this,  that,  or  the  other  variation  fail  to  be  thus 
inherited,  it  is  difficult  to  exclude  the  possibility  of  its 
being  an  acquired  variation  not  truly  innate.  Certainly 
variations  seem  sometimes  to  appear  in  one  generation, 
and  not  to  be  inherited  at  all.  And,  as  we  have  seen,  Mr. 


Organic  Evolution.  225 

Eomanes  appeals  to  a  gradual  failure  of  heredity,  apart 
from  intercrossing,  to  explain  the  diminution  of  disused 
organs. 

That  a  variation  strongly  developed  in  both  parents  is 
apt  to  be  augmented  in  the  offspring  is  commonly  believed 
by  breeders.  Darwin  was  assured  that  to  get  a  good 
jonquil-coloured  canary  it  does  not  answer  to  pair  two 
jonquils,  as  the  colour  then  comes  out  too  strong,  or  is 
even  brown.  Moreover,*  "  if  two  crested  canaries  are  paired, 
the  young  birds  rarely  inherit  this  character ;  for  in  crested 
birds  a  narrow  space  of  bare  skin  is  left  on  the  back  of  the 
head,  where  the  feathers  are  upturned  to  form  the  crest, 
and,  when  both  parents  are  thus  characterized,  the  bare- 
ness becomes  excessive,  and  the  crest  itself  fails  to  be 
developed." 

On  the  whole,  it  would  seem  that  variations  may  either 
be  neutralized  or  augmented  in  inheritance ;  but  the  deter- 
mining causes  are  not  well  understood. 

Another  fact  to  be  noticed  with  regard  to  the  inheritance 
of  variations  is  that  some  characters  blend  in  the  offspring, 
while  others  apparently  fail  to  do  so.  Mr.  Francis  Galton,f 
speaking  of  human  characters,  gives  the  colour  of  the  skin 
as  an  instance  of  the  former,  that  of  the  eyes  as  an 
example  of  the  latter.  If  a  negro  marries  a  white  woman, 
the  offspring  are  mulattoes.  But  the  children  of  a  light- 
eyed  father  and  a  dark-eyed  mother  are  either  light-eyed 
or  dark-eyed.  Their  eyes  do  not  present  a  blended  tint. 
Among  animals  the  colour  of  the  hair  or  feathers  is  often  a 
mean  or  blended  tint ;  but  not  always.  Darwin  gives  the 
case  of  the  pairing  of  grey  and  white  mice,  the  offspring  of 
which  are  not  whitish-grey,  but  piebald.  If  you  cross  a 
white  and  a  black  game  bird,  the  offspring  are  either  black 
or  white,  neither  grey  nor  piebald.  Sir  R.  Heron  crossed 
white,  black,  brown,  and  fawn-coloured  Angora  rabbits,  and 
never  once  got  these  colours  mingled  in  the  same  animal, 
but  often  all  four  colours  in  the  same  litter.  He  also 

*  Darwin,  "  Animals  and  Plants  under  Domestication,"  vol.  i.  p.  465. 
t  "  Natural  Inheritance,"  p.  12. 


226  Animal  Life  and  Intelligence. 

crossed  "  solid-hoofed  "  and  ordinary  pigs.  The  offspring 
did  not  possess  all  four  hoofs  in  an  intermediate  condition  ; 
but  two  feet  were  furnished  with  properly  divided  and  two 
with  united  hoofs.*  Professor  Eimerf  has  noticed  that,  in 
the  crossing  of  striped  and  unstriped  varieties  of  the 
garden  snail,  Helix  hortensis,  the  offspring  are  either  striped 
or  unstriped,  not  in  an  intermediate  or  faintly  striped 
condition. 

These  facts  are  of  no  little  importance.  They  tend  to 
minimize,  for  some  characters  at  least,  the  effects  of  inter- 
crossing. The  variations  which  present  this  trait  may  be 
likened  to  stable  organic  compounds,  which  may  be  in- 
herited or  not  inherited,  but  which  cannot  be  watered  down 
by  admixture  and  intercrossing.  It  is  well  known  J  that, 
in  1791,  a  ram-lamb  was  born  in  Massachusetts,  with 
short,  crooked  legs  and  a  long  back,  like  a  turn-spit  dog. 
From  this  one  lamb  §  the  otter,  or  ancon,  breed  was  raised. 
When  sheep  of  this  breed  were  crossed  with  other  breeds, 
the  lambs,  with  rare  exceptions,  perfectly  resembled  one 
parent  or  the  other.  Of  twin  lambs,  even,  one  has  been 
found  to  resemble  one  parent,  and  the  second  the  other. 
All  that  the  breeder  has  to  do  is  to  eliminate  those  which 
do  not  possess  the  required  character.  And  very  rarely 
do  the  lambs  of  ancon  parents  fail  to  be  true-bred. 

Now,  it  can  scarcely  fail  that  such  sports  occur  in 
nature.  And  if  they  are  stable  compounds,  they  will  not 
be  readily  swamped  by  intercrossing.  It  only  requires  some 
further  isolation  to  convert  the  sporting  individuals  into  a 
distinct  and  separate  variety.  Now,  Darwin  tells  us  that 

*  Darwin,  "  Animals  and  Plants  under  Domestication,"  vol.  ii.  p.  70. 

t  "  Organic  Evolution,"  Mr.  Cunningham's  translation,  p.  76. 

J  Darwin,  "  Animals  and  Plants  uuder  Domestication,"  vol.  i.  p.  104. 

§  Similarly,  from  a  chance  sport  of  a  one-eared  rabbit,  Anderson  formed  a 
breed  which  steadily  produced  one-eared  rabbits  ("  Animals  and  Plants  under 
Domestication,"  vol.  i.  p.  456).  This  is  an  example  of  asymmetrical  variation. 
Variations  are  generally,  but  not  always,  symmetrical.  Superficial  colour- 
variations  are  sometimes  asymmetrical.  Gasteropod  molluscs  are  nearly 
always  asymmetrically  developed.  Among  insects,  Anisognathus  affords  an 
example  of  the  asymmetrical  development  of  the  mandible.  Our  right-handed- 
ness is  a  mark  of  asymmetry. 


Organic  Evolution.  227 

the  ancons  have  been  observed  to  keep  together,  separating 
.  themselves  from  the  rest  of  the  flock  when  put  into 
enclosures  with  other  sheep.  Here,  then,  we  have  pre- 
ferential mating  as  the  further  isolating  factor.  I  feel 
disposed,  therefore,  to  agree  with  Mr.  Galton  when  he 
says,*  "  The  theory  of  natural  selection  might  dispense 
with  a  restriction  for  which  it  is  difficult  to  see  either  the 
need  or  the  justification,  namely,  that  the  course  of  evolu- 
tion always  proceeds  by  steps  that  are  severally  minute, 
and  that  become  effective  only  through  accumulation. 
That  the  steps  may  be  small,  and  that  they  must  be  small, 
are  very  different  views ;  it  is  only  to  the  latter  that  I 
object,  and  only  when  the  indefinite  word  '  small '  is  used 
in  the  sense  of  '  barely  discernible,'  or  as  small  as  com- 
pared with  such  large  sports  as  are  known  to  have  been 
the  origins  of  new  races." 

Connected,  perhaps,  with  the  phenomena  we  have  just 
been  considering  is  that  of  prepotency .f  It  is  found  that, 
when  two  individuals  of  the  same  race  or  of  different  races 
are  crossed,  one  has  a  preponderant  influence  in  deter- 
mining the  character  of  the  offspring.  Thus  the  famous 
bull  Favourite  is  believed  to  have  had  a  prepotent  influence 
on  the  short-horn  race ;  and  the  improved  short-horns 
possess  great  power  in  impressing  their  likeness  on  other 
breeds.  The  phenomena  are  in  some  respects  curiously 
variable.  In  fowls,  silkiness  of  feathers  seems  to  be  at 
once  bred  out  by  intercrossing  between  silk-fowl  and  any 
other  breed.  But  in  the  silky  variety  of  the  fan-tail 
pigeon  this  character  seems  prepotent ;  for,  when  the 
variety  is  crossed  with  any  other  small-sized  race,  the 
silkiness  is  invariably  transmitted.  One  may  fairly  sup- 
pose that  prepotent  characters  have  unusual  stability; 
but  to  what  causes  this  stability  is  due  we  are  at  present 
ignorant. 

Lastly,  we  have  to  consider  the  phenomenon  of  latency. 

*  "  Natural  Inheritance,"  p.  32. 

f  See  "  Animals  and  Plants  under  Domestication,"  vol.  ii.   p.  40,  from 
which  illustrations  are  taken. 


228  Animal  Life  and  Intelligence. 

This  is  the  lying  hid  of  characters  and  their  subsequent 
emergence.     We  may  distinguish  three  forms  of  latency. 

1.  Where  characters  lie  hid  till  a  certain  period  of  life, 
and  then  normally  emerge. 

2.  Where  the  characters  normally  lie  hid  throughout 
life,   but    are,   under    certain   circumstances,   abnormally 
developed. 

8.  Where  the  characters  lie  hid  throughout  life,  but 
appear  in  the  offspring  or  (sometimes  distant)  descendants. 

Latency  is  often  closely  connected  with  correlated 
variations.  Secondary  sexual  characters,  for  example,  are 
correlated  with  the  functional  maturity  or  activity  of  the 
reproductive  organs.  They  therefore  lie  hid  until  these 
organs  are  mature  and  ready  for  activity.  When  they 
are  restricted  to  the  male,  they  normally  remain  latent 
throughout  the  life  of  the  female,  but  reappear  in  her  male 
offspring.  Under  abnormal  conditions,  such  as  the  removal 
of  the  essentially  male  organs,  the  secondary  sexual  charac- 
ters correlated  with  them  do  not  appear,  or  appear  in  a 
lessened  and  modified  form.  The  males  may  even,  under 
such  circumstances,  acquire  female  characters.  Thus 
capons  take  to  sitting,  and  will  bring  up  young  chickens. 
Conversely,  females  which  have  lost  their  ovaries  through 
disease  or  from  other  causes  sometimes  acquire  secondary 
sexual  characters  proper  to  the  male.  Characters  thus 
normally  latent  abnormally  emerge.  Mr.  Bknd  Button* 
gives  a  case  of  a  hen  golden  pheasant  which  "  presented 
the  resplendent  dress  of  the  cock,  but  her  plumage  was  not 
quite  so  brilliant ;  she  had  no  spurs,  and  the  iris  was  not 
encircled  by  the  ring  of  white  so  conspicuous  in  the  male." 
Her  ovary  was  no  larger  than  a  split  pea. 

A  curious  instance  of  latent  characters  correlated  with 
sex  is  seen  in  hive  bees.  The  worker  bee  differs  from  the 
female  in  the  rudimentary  condition  of  the  sexual  organs, 
in  size  and  form,  and  in  the  higher  development  of  the 
sense-organs.  But  it  is  well  known  that,  if  a  very  young 
worker  grub  be  fed  on  "  royal  jelly,"  she  will  develop  into 

*  "  Evolution  and  Disease,"  p.  169. 


Organic  Evolution.  229 

a  perfect  queen.  Not  only  are  the  sexual  organs  stimulated 
to  increased  growth  and  functional  activity,  but  the  corre- 
lated size  and  condition  of  the  sense-organs  are  likewise 
acquired.  The  characters  of  queen  and  worker  are  latent 
in  the  grub.  According  to  the  nature  of  the  food  it  receives, 
the  one  set  of  characters  or  the  other  emerges.  Professor 
Yung's  tadpoles  and  Mrs.  Treat's  butterflies  (ante,  p.  59) 
afford  similar  instances. 

We  come  now  to  those  cases  of  latency  in  which  this 
obvious  correlation  does  not  occur.  They  afford  examples 
of  reversion  to  more  or  less  remote  ancestral  characters. 
In  some  cases  the  cause  of  such  reversion — such  unexpected 
emergence  of  characters,  which  have  remained  latent 
through  several,  perhaps  many,  generations — is  quite  un- 
known. In  others, "  at  any  rate  among  domesticated 
animals,  the  determining  condition  of  such  reversion  is  the 
crossing  of  distinct  breeds. 

Darwin  gives  *  an  instance  of  reversion,  on  the  authority 
of  Mr.  E.  Walker.  He  bought  a  black  bull,  the  son  of  a 
black  cow  with  white  legs,  white  belly,  and  part  of  the  tail 
white;  and  in  1870  a  calf,  the  gr-gr-gr-gr-grandchild  of 
this  cow,  was  born,  coloured  in  the  same  very  peculiar 
manner,  all  the  intermediate  offspring  having  been  black. 
In  man  partial  reversions  are  not  infrequent.  An  addi- 
tional pair  of  lumbar  ribs  is  sometimes  developed,  and  in 
such  cases  the  fan-shaped  tendons  which  are  normally 
connected  with  the  transverse  processes  of  the  vertebra  are 
replaced  by  functional  levator  muscles.  Since  it  is  probable 
that  the  ancestor  of  man  had  more  than  the  twelve  pairs 
of  ribs  that  are  normally  present  in  the  human  species, 
we  may,  perhaps,  fairly  regard  the  supernumerary  rib  as  a 
reversion.  But  it  may  be  a  new  sport  on  old  lines. 

The  occasional  occurrence  in  Scotland  of  red  grouse 
with  a  large  amount  of  white  in  the  winter  plumage, 
especially  on  the  under  parts,  is  justly  regarded  by  Mr. 
Wallace  t  as  a  good  example  of  reversion  or  latency  in 

*  "  Animals  and  Plants  under  Domestication,"  vol.  ii.  p.  8. 
f  "  Darwinism,"  p.  107. 


230  Animal  Life  and  Intelligence. 

wild  birds.  There  can  be  little  doubt  that,  as  he  suggests, 
the  Scotch  red  grouse  is  derived  from  a  form  which,  like 
the  wide-ranging  willow  grouse,  has  white  winter  plumage. 
During  the  glacial  epoch  this  would  be  an  advantage. 
"  But  when  the  cold  passed  away,  and  our  islands  became 
permanently  separated  from  the  mainland,  with  a  mild 
and  equable  climate,  and  very  little  snow  in  winter,  the 
change  to  white  at  that  season  became  hurtful,  rendering 
the  birds  more  conspicuous,  instead  of  serving  as  a  means 
of  concealment."  The  red  grouse  has  lost  its  white  winter 
dress ;  but  occasional  reversions  point  to  the  ancestral 
habit. 

That  crossing  tends  to  produce  reversion  is  a  fact 
familiar  to  breeders  and  fanciers,  and  one  which  is 
emphasized  by  Darwin.  When  pigeons  are  crossed,  there 
is  a  strong  tendency  to  revert  to  the  slatey-blue  tint  and 
black  bars  of  the  ancestral  rock-pigeon.  There  is  always 
a  tendency  in  sheep  to  revert  to  a  black  colour,  and  this 
tendency  is  emphasized  when  different  breeds  are  crossed. 
The  crossing  of  the  several  equine  species  (horse,  ass,  etc.) 
"  tends  in  a  marked  manner  to  cause  stripes  to  appear  on 
various  parts  of  the  body,  especially  on  the  legs,"  and  this 
may  be  a  reversion  to  the  condition  of  a  striped  and  zebra- 
like  ancestor.  Professor  Jaeger  described  a  good  case  with 
pigs.  "  He  crossed  the  Japanese,  or  masked  breed,  with 
the  common  German  breed,  and  the  offspring  were  inter- 
mediate in  character.  He  then  recrossed  one  of  these 
mongrels  with  a  pure  Japanese,  and  in  the  litter  thus 
produced  one  of  the  young  resembled  in  all  its  characters 
a  wild  pig  ;  it  had  a  long  snout  and  upright  ears,  and  was 
striped  on  the  back.  It  should  be  borne  in  mind  that  the 
young  of  the  Japanese  breed  are  not  striped,  and  that  they 
have  a  short  muzzle  and  ears  remarkably  dependent."  * 
Darwin  crossed  a  black  Spanish  cock  with  a  white  silk  hen. 
One  of  the  offspring  almost  exactly  resembled  the  Gallus 
bankiva,  the  remote  ancestor  of  the  parents. 

Such  cases  would  seem  to  show  that  in  our  domestic 

*  Darwin,  "  Animals  and  Plants  under  Domestication,"  vol.  ii.  pp.  17,  18. 


Organic  Evolution.  231 

breeds  ancestral  traits  lie  latent.  The  crossing  of  distinct 
varieties  may  either  neutralize  the  variations  artificially 
selected,  and  thus  allow  the  ancestral  characters  which 
have  been  masked  by  them  to  reappear ;  or  they  may 
allow  the  elements  of  the  ancestral  traits,  long  held  apart 
in  separate  breeds  by  domestication,  to  recombine  with  the 
consequent  emergence  of  the  normal  characters  of  the  wild 
species.  But,  in  truth,  any  attempted  explanations  of  the 
facts  are  little  better  than  guess-work.  There  are  the 
facts.  And  the  importance  of  crossing  as  a  determining 
condition  in  domesticated  animals  should  make  us  cautious 
in  applying  reversion,  as  it  occurs  in  such  cases,  to  wild 
species  which  live  under  more  stable  conditions  where 
crossing  is  of  rare  occurrence. 


The  Origin  of  Variations.     ^  * 

The  subject  of  the  origin  of  variations  is  a  difficult  one, 
one  concerning  which  comparatively  little  is  known,  and 
one  on  which  I  am  not  able  to  throw  much  light. 

Taking  a  simple  animal  cell  as  our  starting-point,  we 
have  already  seen  that  it  performs,  in  primitive  fashion, 
certain  elementary  and  essential  protoplasmic  activities, 
and  gives  rise  to  certain  products  of  cell-life.  In  the 
metazoa,  which  are  co-ordinated  aggregates  of  animal 
cells,  together  with  some  of  their  products,  there  is  seen  a 
division  of  labour  and  a  differentiation  of  structure  among 
the  cells.  We  see,  then,  that  variation  among  these  related 
cells  has  led  to  differences  in  size,  in  form,  in  transparency, 
and  in  function  ;  while  the  cell-products  have  been  differ- 
entiated into  those  which  are  of  lifelong  value,  such  as 
bone,  cartilage,  connective  tissue,  horn,  chitin,  etc., 
together  with  a  variety  of  colouring  matters  ;  those  which 
are  of  temporary  value,  such  as  the  digestive  secretions, 
fat,  etc. ;  and  those  which  are  valueless  or  noxious,  such  as 
carbonic  acid  gas  and  urea,  which  are  excreted  as  soon  as 
possible.  Here  are  already  a  number  of  important  and 
fundamental  variations  to  be  accounted  for. 


232  Animal  Life  and  Intelligence. 

Let  us  notice  that,  wide  as  the  variations  are,  they  are  / 
to  a  large  extent  hedged  in  by  physical,  chemical,  and/ 
organic  limitations.  We  have  already  seen  that  the  size 
of  cells  is  to  a  large  extent  limited,  because  during  growth 
mass  tends  to  outrun  surface ;  and  because,  while  disrup- 
tive changes  occur  throughout  the  mass,  nutriment  and 
oxygen  must  be  absorbed  by  the  surface.  This  is  a 
physical  limitation.  Since  the  products  of  cell-life  and 
cell-activity  are  chemical  products,  it  is  clear  that  they  can 
only  be  produced  under  the  fixed  limitations  of  chemical 
combination ;  and  though  in  organic  products  these  limi- 
tations are  not  so  rigid  as  among  inorganic  substances, 
still  that  there  are  limitations  no  chemist  is  likely  to 
question.  The  organic  limitations  are  to  the  varied,  but 
not  very  numerous,  modes  of  protoplasmic  activity. 

Probably,  even  at  the  threshold  of  metazoan  life,  such 
variations  did  not  affect  only  individual  cells,  but  rather 
groups  of  cells.     In  other  words,  the  differentiation  was  at 
once  and  primarily  a  tissue-differentiation.     What  do  we 
know,  however,  about  the  primitive  tissue-differentiation  of 
the  earliest  metazoa  ?    Hardly  anything.     We  may  fairly 
suppose  that  the  first  marked  difference  to  appear  was 
that  between  the  outside  and  the  inside.     In  the  formation 
of  an  embryo  this  is  the  first   differentiation  we  notice. 
From  the  beginning  of  segmentation  or,  in  any  case,  very 
early,  the  outer-layer  cells  become  marked  off  from  the 
inner-layer  cells.     The  next  step  was,  perhaps,  the  forma- 
tion of  the  mid-layer  between  the  outer  and  inner.     But 
how  further  differentiations  were  effected  we  really  do  not 
know,  though  we  may  guess  a  little.     This,  perhaps,  we 
may  fairly  surmise — that  fresh  differentiations  presupposed 
previous  differentiations,  and  formed  the  basis  of  yet  further 
differentiations.     Thus  calcified  cartilage  presupposes  car- 
tilage, and  leads  up  to  the  formation  of  true  bone.     In  all 
this,  however,  we  .are  very  much  in  the  dark.     We  can 
watch,  always  with  fresh  wonder,  the  genesis  of  tissues  in 
the  development  of  the  embryo ;  but  we  do  not  at  present 
know  much  of  the  mode  of  their  primitive  genesis  in  the 


Organic  Evolution.  233 


early  days  of  organic  evolution:   how  can  we,  then,  pre- 
tend to  understand  their  origins  ? 

If  we  speculate  at  all  on  the  matter,  we  are  led  to  the 
view  that  the  variations  must  be  primarily  due  to  the 
differential  incidence  of  mechanical  stresses  and  physical 
or  chemical  influences.  It  may  be  admitted  that  this  is 
little  more  than  saying  that  they  are  due  to  some  physical 
cause.  Still,  this  at  least  may  be  taken  as  certain  for 
what  it  is  worth — that  the  primitive  tissue-differentiations 
are  due  to  physical  or  chemical  influences,  direct  or  indirect, 
on  the  protoplasm  of  the  cell.  Here  is  one  mode  of  the 
origin  of  variations. 

I  do  not  wish  to  reopen  the  question  whether  these" 
variations  originate  in  the  germ  or  in  the  body.  I  content 
myself  with  indicating  the  difference,  from  this  standpoint, 
between  the  two  views.  Take,  for  example,  the  end-organs 
of  the  special  senses,  which  respond  explosively  to  physical 
influences  in-  ways  we  shall  have  to  consider  more  fully  in 
the  next  chapter.  If  we  hold  that  variations  originating 
in  the  body  may  be  transmitted  through  the  germ  to  the 
offspring,  then  we  may  say  that  these  variations  are  the 
direct  result  of  the  incidence  of  the  physical  or  molecular 
vibrations  on  the  protoplasm.  But  if  we  believe,  with 
Professor  Weismann,  that  all  variations  originate  in  the 
germ,  then  the  variations  in  the  end-organs  of  the  special 
senses,  fitting  them  to  be  the  recipients  of  special  modes  of 
influence,  result  from  physical  effects  upon  the  germ  of 
purely  fortuitous  origin,  that  is  to  say,  wholly  unrelated  to 
the  end  in  view.  The  rods  and  cones  of  the  retina  are  due 
to  purely  chance  variations,  impressed  by  some  chemical 
or  physical  causes  completely  unknown  on  the  germinal 
protoplasmic  substance.  Those  individuals  which  did  not 
have  these  chance  variations  have  been  eliminated.  It 
matters  not  that  the  rods  and  cones  are  believed  to  have 
reached  their  present  excellence  through  many  intermediate 
steps  from  much  simpler  beginnings.  The  fact  remains 
that  the  origin  of  all  these  step-like  variations  was  fortui- 
tous, and  not  in  any  way  the  direct  outcome  of  the  physical 


234  Animal  Life  and  Intelligence. 

influences  which  their  products,  the  rods  and  cones,  have 
become  fitted  to  receive.   I  am  not  at  present  prepared  to  ac-    > 
ceptthis  theory  of  the  germinal  origin  of  all  tissue-variations./ 

Whether  use  and  disuse  are  to  be  regarded  as  sources 
of  origin  of  variations  is,  again,  a  matter  in  which  there 
is  wide  difference  of  opinion.  But  if  we  admit  that  any 
variations  can  take  their  origin  in  the  body  (as  dis- 
tinguished from  the  germ),  then  there  is  no  a  priori  reason 
for  rejecting  use  and  disuse  as  factors.  As  such,  we  are,  I 
think,  justified,  in  the  present  state  of  our  knowledge,  in 
reckoning  them,  at  all  events,  provisionally. 

It  is  clear,  however,  that  they  are  a  proximate,  not  an 
ultimate,  source  of  origin.  I  mean  that  the  structures 
must  be  there  before  they  can  be  either  strengthened  or 
weakened  by  use  or  disuse.  They  are  at  most  a  source  of 
positive  or  negative  variations  of  existing  structures.  They 
cannot  be  a  direct  source  of  origin  of  superficial  variations. 
Gain  or  loss  of  colour ;  form-variations  not  correlated  with 
organic  variations  ; — these  cannot  be  directly  due  to  use  or 
disuse.  It  is  in  the  nervous  and  muscular  systems  and  the 
glandular  organs  that  use  and  disuse  are  mainly  operative. 
When,  however,  organs  are  brought  into  relation,  or  fail  to 
be  brought  into  relation,  to  their  appropriate  stimuli,  we 
speak  of  this,  too,  as  use  and  disuse.  We  say,  for  example, 
that  persistent  disuse  may  impair  the  essential  tissues  of 
the  recipient  end-organs  of  the  special  senses,  implying 
that  these  tissues  require  to  be  brought  into  continued 
relation  to  the  appropriate  stimuli  in  order  that  their 
efficiency  be  maintained.  So,  too,  we  say  that  the  epidermis 
is  thickened  by  use,  meaning  that  it  is  brought  into  rela- 
tion with  certain  mechanical  stresses.  Through  correlation, 
too,  the  effects  of  use  and  disuse  may  be  widespread.  Thus 
increase  in  the  size  of  a  group  of  muscles  may  be  correlated 
with  increase  in  the  size  of  the  bones  to  which  they  are  in 
relation.  In  fact,  so  knit  together  and  co-ordinated  is  the 
organism  into  a  unity,  it  is  probable  that  hardly  any 
variation  could  take  place  through  use  or  disuse  without 
modifying  to  some  extent  the  whole  organic  being. 


Organic  Evolution.  235 

Once  more,  let  it  be  clearly  remembered  that  a  large 
and  important  school  of  zoologists  reject  altogether  use  or 
disuse  as  a  factor  in  variation.  They  believe  that  those 
germs  are  selected  through  natural  selection  in  which 
there  is  an  increased  tendency  to  use  or  disuse  of  certain 
organs.  In  this,  however,  we  are  all  agreed.  The  real 
question  is  what  is  the  source  of  origin  of  this  tendency. 
On  the  view  of  germinal  origin,  we  are  forced  back  on 
unknown  physical  or  chemical  influences  in  no  wise  related 
in  origin  (though,  of  course,  related  in  result)  with  the  use 
or  disuse  to  which  they  give  rise. 

So  far  the  main  distinction  between  the  two  biological 
schools  seems  to  be  that  the  one,  placing  the  origin  of 
variation  in  the  body-tissues,  regards  the  variations  as 
evoked  in  direct  reaction  to  physical  or  chemical  influences  ; 
while  the  other,  placing  the  origin  of  variation  in  the 
germ,  regards  the  variations  as  of  fortuitous  origin. 

I  do  not  use  the  phrase,  "  of  fortuitous  origin,"  as  in 
any  sense  discrediting  the  theory.  I  am  not  attempting 
the  cheap  artifice  of  damning  a  view  that  does  not  happen 
to  be  my  own  with  a  phrase  or  a  nickname.  And  I  there- 
fore hasten  to  point  out  what  variations  I  do  believe  to 
have  had  a  fortuitous  origin.  The  phrase  is  often  mis- 
understood, and  they  will  serve  to  explain  its  meaning. 

If  the  reader  will  kindly  refer  to  the  tables  of  variations 
in  the  bats'  wings  (Figs.  14-17),  he  will  see  that  there  are 
a  great  number  of  bones  which  vary  in  length  and  vary 
independently.  And  if  he  will  also  refer  to  Fig.  18,  in 
which  seven  species  of  bats  are  compared,  he  will  see  that 
the  differences  arise  from  the  increased  length  of  one  set 
of  bones  in  one  species  and  another  set  of  bones  in  another 
species.  Now,  let  us  suppose  that  the  long,  swallow-like 
wing  of  the  noctule,  a  high  flyer  with  rapid  wing-strokes, 
that  catches  insects  in  full  flight,  and  the  broad  wings  of 
the  horse-shoe,  a  low  flyer,  flapping  slowly,  and,  at  any 
rate,  sometimes  catching  insects  on  the  ground,  and  cover- 
ing them  with  its  wings  as  with  a  net ;  let  us  suppose,  I 
say,  that  to  each  species  its  special  form  of  wing  is  an 


236  Animal  Life  and  Intelligence. 

advantage.  Among  thousands  of  independent  variations 
in  the  lengths  of  the  bones  there  would  be  occasional  com- 
binations of  variations,  giving  either  increased  length  or 
increased  breadth  to  the  wing.  In  the  noctule,  the  former 
would  tend  to  be  selected;  in  the  horse-shoe,  the  latter. 
Thus  the  wing  of  the  noctule  would  be  lengthened,  and  that 
of  the  horse-shoe  broadened,  through  the  selection  of  for- 
tuitous combinations  of  variations  which  chanced  to  be 
favourable.  Now,  each  individual  bone-variation  is,  we 
believe,  due  to  some  special  cause ;  but  the  fortunate  com- 
bination is  fortuitous,  due  to  what  we  term  "  mere  chance." 

Darwin  believed  that  chance,  in  this  sense,  played  a 
very  important  part  in  the  origin  of  those  favourable 
variations  for  which,  as  he  said,  natural  selection  is  con- 
stantly and  unceasingly  on  the  watch.  And  there  can  be 
little  question  that  Darwin  was  right. 

We  must  now  consider  very  briefly  some  of  the  proxi- 
mate causes  of  variations.  In  most  of  these  cases  we 
cannot  hope  to  unravel  the  nexus  of  causation.  When  a 
plexus  of  environing  circumstances  acts  upon  a  highly 
organized  living  animal,  the  most  we  can  do  in  the  present 
state  of  knowledge  is  to  note — we  cannot  hope  to  explain — 
the  effects  produced. 

All  readers  of  Darwin's  works  know  well  how  insistent 
he  was  that  the  nature  of  the  organism  is  more  important 
than  the  nature  of  the  environing  conditions.  "  The 
organization  or  constitution  of  the  being  which  is  acted 
on,"  he  says,*  "is  generally  a  much  more  important 
element  than  the  nature  of  the  changed  conditions  in 
determining  the  nature  of  the  variation."  And,  again, t 
"  We  are  thus  driven  to  conclude  that  in  most  cases  the 
conditions  of  life  play  a  subordinate  part  in  causing  any 
particular  modification ;  like  that  which  a  spark  plays 
when  a  mass  of  combustible  matter  bursts  into  flame — the 

*  "  Animals  and  Plants  under  Domestication,"  vol.  ii.  p.  201. 

f  Ibid.  p.  282.  The  phenomena  of  the  seasonal  dimorphism  of  butterflies 
and  moths  show  that  changes  of  temperature  (and  perhaps  moisture,  etc.) 
determine  very  strikiug  differences  in  these  insects. 


Organic  Evolution.  237 

nature  of  the  flame  depending  on  the  combustible  matter, 
and  not  on  the  spark." 

Eecent  investigations  have  certainly  not  lessened  the 
force  of  Darwin's  contention.  From  which  there  follows 
the  corollary  that  the  vital  condition  of  the  organism  is  a 
fact  of  importance.  Darwin  was  led  to  believe  that  among 
domesticated  animals  and  plants  good  nutritive  conditions 
were  favourable  to  variation.  "  Of  all  the  causes  which 
induce  variability,"  he  says,*  "  excess  of  food,  whether  or 
not  changed  in  nature,  is  probably  the  most  powerful." 
Darwin  also  held  that  the  male  is  more  variable  than  the 
female — a  view  that  has  been  especially  emphasized  by 
Professor  W.  K.  Brooks.  Mr.  Wallace,  as  we  have  already 
seen,  regards  the  secondary  sexual  characters  of  male  birds 
as  the  direct  outcome  of  superabundant  health  and  vigour. 
"There  is,"  he  says,f  "in  the  adult  male  a  surplus  of 
strength,  vitality,  and  growth-power  which  is  able  to 
expend  itself  in  this  way  without  injury."  And  Messrs. 
Geddes  and  Thomson  contend \  that  "  brilliancy  of  colour, 
exuberance  of  hair  and  feathers,  activity  of  scent-glands, 
and  even  the  development  of  weapons,  are  in  origin  and 
development  outcrops  of  a  male  as  opposed  to  a  female 
constitution." 

There  is,  I  think,  much  truth  in  these  several  views 
thus  brought  into  apposition.  Vigour  and  vitality,  pre- 
dominant activity  and  the  consequent  disruptive  changes, 
with  their  abundant  by-products  utilized  in  luxuriant  out- 
growths and  brilliant  colours,  are  probably  important 
sources  of  variation.  They  afford  the  material  for  natural 
selection  and  sexual  selection  to  deal  with.  These  guide 
the  variations  in  specific  directions.  For  I  am  not  pre- 
pared to  press  the  theory  of  organic  combination  so  far  as 
to  believe  that  this  alone  has  served  to  give  definiteness 
to  the  specific  distinctions  between  secondary  sexual  charac- 
ters, though  it  may  have  been  to  some  extent  a  co-operating 
factor.  This,  however,  is  a  question  apart  from  that  of 

*  "  Animals  and  Plants  under  Domestication,"  vol.  ii.  p.  244. 

t  "  Darwinism,"  p.  293.  J  "  Evolution  of  Sex,"  p.  22. 


238  Animal  Life  and  Intelligence. 

origin.  Superabundant  vigour  may  well,  I  think,  have 
been  a  source  of  origin,  not  only  of  secondary  sexual  charac- 
ters, but  of  many  other  forms  of  variation. 

And  while  these  forms  of  variation  may  be  the  special 
prerogative  of  the  male,  we  may  perhaps  see,  in  super- 
abundant female  vigour,  a  not  less  important  source  of 
developmental  and  embryonic  variations  in  the  offspring. 
The  characteristic  selfishness  of  the  male  applies  his  surplus 
vitality  to  the  adornment  of  his  own  person;  the  charac- 
teristic self-sacrifice  of  the  mother  applies  her  surplus 
vitality  to  the  good  of  her  child.  Here  we  may  have  the 
source  and  origin  of  those  variations  in  the  direction  of 
fosterage  and  protection  which  we  have  seen  to  have  such 
important  and  far-reaching  consequences  in  the  develop- 
ment of  organic  life.  The  storage  of  yolk  in  the  ovum,  the 
incubation  of  heavily  yolked  eggs,  the  self-sacrificing  de- 
velopment in  the  womb,  the  elaboration  of  a  supply  of 
food-milk, — all  these  and  other  forms  of  fosterage  may  well 
have  been  the  outcome  of  superabundant  female  vigour, 
the  advantages  of  which  are  thus  conferred  upon  the 
offspring. 

We  may  now  proceed  to  note,  always  remembering  the 
paramount  importance  of  the  organism,  some  of  the  effects 
produced  by  changes  in  the  environment. 

The  most  striking  and  noteworthy  feature  about  the 
effects  of  changes  of  climate  and  moisture,  changes  of 
salinity  of  the  water  in  aquatic  organisms,  and  changes 
of  food-stuff,  is  that,  when  they  produce  any  effect  at 
all,  they  give  rise  to  definite  variations.  Only  one  or 
two  examples  of  each  can  here  be  cited.  Mr.  Merrifield,* 
experimenting  with  moths  (Selenia  illunaria  and  S.  illus- 
traria),  finds  that  the  variations  of  temperature  to  which 
the  pupae,  and  apparently  also  the  larvae,  are  subjected 
tend  to  produce  "very  striking  differences  in  the  moths." 
On  the  whole,  cold  "  has  a  tendency,  operating  possibly 
by  retardation,  to  produce  or  develop  a  darker  hue  in 

*  "Incidental  Observations  in  Pedigree  Moth-breeding,"  F.  Merrifield. 
Transactions  Entomological  Society,  1889,  pt.  i.  p.  79,  et  neq. 


Organic  Evolution.  239 


the  perfect  insect ;  if  so,  it  may,  perhaps,  throw  some 
light  on  the  melanism  so  often  remarked  in  north-country 
examples  of  widely  distributed  moths."  Mr.  Cockerell* 
regards  moisture  as  the  determining  condition  of  a  certain 
phase  of  melanism,  especially  among  Lepidoptera.  The 
same  author  states  that  the  snail  "Helix  nemoralis  was 
introduced  from  Europe  into  Lexington,  Virginia,  a  few 
years  ago.  Under  the  new  conditions  it  varied  more  than 
I  have  ever  known  it  to  do  elsewhere,  and  up  to  the 
present  date  (1890)  125  varieties  have  been  discovered 
there.  Of  these,  no  less  than  67  are  new,  and  unknown 
in  Europe,  the  native  country  of  the  species."  The  effects 
of  the  salinity  of  the  water  on  the  brine-shrimp  Artemia 
have  already  been  mentioned.  One  species  with  certain 
characteristics  was  transformed  into  another  species  with 
other  characteristics  by  gradually  altering  the  saltness  of 
the  water.  So,  too,  in  the  matter  of  food,  the  effects  of 
feeding  the  caterpillars  of  a  Texan  species  of  Saturnia  on 
a  new  food-plant  were  so  marked  that  the  moths  which 
emerged  were  reckoned  by  entomologists  as  a  new  species. 
The  point,  I  repeat,  to  be  especially  noted  about  these 
cases  and  others  which  might  be  cited, f  is  that  the  varia- 
tion produced  is  a  definite  variation.  Very  probably  it  is 
generally,  or  perhaps  always,  produced  in  the  embryonic 
or  larval  period  of  life.  In  some  cases  the  variation  seems 
to  be  transmissible,  though  definite  and  satisfactory  proofs 
of  this  are  certainly  wanting.  Still,  we  may  say  that  if 
the  changed  conditions  be  maintained,  the  resulting  varia- 
tion will  also  be  maintained.  Under  these  conditions,  at 
least,  the  variation  is  a  stable  one.  It  is  probable  that, 
apart  from  preferential  mating,  the  varieties  thus  produced 
will  tend  to  breed  together  rather  than  to  be  crossed  with 
the  parent  form  or  varieties  living  under  different  con- 
ditions. In  this  way  varieties  may  sometimes  arise  by 

*  Nature,  vol.  xli.  p.  393. 

t  See  Professor  Meldola's  edition  of  Professor  Weismann's  "  Studies  in 
the  Theory  of  Descent,"  and  Mr.  Cunningham's  translation  of  Professor 
Elmer's  "  Organic  Evolution." 


240  Animal  Life  and  Intelligence. 

definite  and  perhaps  considerable  leaps  under  the  influence 
of  changed  conditions.  We  must  not  run  the  adage,  Natura 
nil  facit  per  saltum,  too  hard,  nor  interpret  saltum  in  too 
narrow  a  sense. 

It  is  true,  and  we  may  repeat  the  statement  of  the  fact 
for  the  sake  of  emphasis,  that  we  do  not  know  how  or  why 
this  or  that  particular  variation  should  result  from  this  or 
that  change  of  climate,  environment,  or  food-stuff ;  nor  do 
we  know  why  certain  variations  (such  as  that  which  pro- 
duced the  ancon  breed  of  sheep)  should  be  stable,  while 
other  variations  are  peculiarly  unstable.  But  in  this  we 
are  not  worse  off  than  we  are  in  the  study  of  inorganic 
nature.  We  do  not  know  why  calcite  should  crystallize  in 
any  particular  one  of  its  numerous  varieties  of  crystalline 
form ;  we  do  not  know  why  some  of  these  are  more  stable 
than  others.  We  may  be  able  to  point  to  some  of  the 
conditions,  but  we  cannot  be  said  to  understand  why 
arragonite  should  be  produced  under  some  circumstances, 
calcite  under  others  ;  or  why  the  same  constituents  should 
assume  the  form  of  augite  in  some  rocks,  and  hornblende 
in  other  rocks.  We  are  hedged  in  by  ignorance;  and 
perhaps  one  of  our  chief  dangers,  becoming  with  some 
people  a  besetting  sin,  is  that  of  pretending  to  know  more 
than  we  are  at  present  in  a  position  to  know.  Our  very 
analogies  by  which  we  endeavour  to  make  clear  our  mean- 
ing may  often  seem  to  imply  an  unwarrantable  assumption 
of  knowledge. 

In  the  last  chapter  I  used  the  term  "  organic  combina- 
tion," and  drew  a  chemical  analogy.  I  wished  to  indicate 
the  particularity  and  the  stability  of  certain  variations,  and 
the  possibility  of  new  departures  through  new  combinations 
of  variations,  the  new  departure  not  being  necessarily  any- 
thing like  a  mean  between  the  combining  variations.*  I 
trust  that  this  will  not  be  misunderstood  as  a  new  chemico- 
physical  theory  of  organic  forms.  I  have  some  fear  lest  I 
should  be  represented  as  maintaining  that  a  giraffe  or  a 
peacock  is  a  definite  organic  compound,  with  its  proper 

*  See  Darwin,  "  Animals  and  Plants  under  Domestication,"  vol.  ii.  p.  252. 


Organic  Evolution.  241 

organic  form,  in  exactly  the  same  way  as  a  rhombohedron 
of  calcite  or  a  rhombic  dodecahedron  of  garnet  is  a  definite 
chemical  compound,  with  its  proper  crystalline  form.  All 
that  the  analogy  is  intended  to  convey  is  that  variations 
seem,  under  certain  circumstances,  to  be  definite  and  stable, 
and  may  possibly  combine  rather  than  commingle. 

\ 

Summary  and  Conclusion. 

It  only  remains  to  bring  this  chapter  to  a  close  with  a 
few  words  of  summary  and  conclusion. 

The  diversity  of  animal  life  must  first  be  grasped.  We 
believe  that  this  diversity  is  the  result  of  a  process  or 
processes  of  evolution.  Evolution  is  the  term  applied  tojj 
continuity  of  development.  It  involves  adaptation ;  and 
adaptation  to  an  unchanging  environment  may  become 
more  and  more  perfect.  But  the  environment  to  which 
organisms  are  adapted  also  changes.  Where  thp,  change  is 
in  the  direction  of  complexity,  we  have  elaboration ;  where 
it  is  in  the  direction  of  simplicity,  we  have  degeneration,  [ 
Of  these  elaboration  is  the  more  important.  It  involves 
both  a  tendency  to  differentiation  giving  rise  to  indi- 
viduality, and  a  tendency  to  integration  giving  rise  to 
association.  Continued  elaboration  is  progress  ;  and  this 
is  opposed  to  degeneration. 

The  factors  of  evolution  fall  under  two  heads — origin 
and  guidance.  The  origin  of  variations  lies  in  mechanical 
stresses,  and  chemical  or  physical  influences.  Whether 
these  act  on  the  body  (and  are  transmitted  by  inheritance) 
or  only  on  the  germ,  is  a  question  which  divides  biologists 
into  two  schools.  In  the  latter  case  all  variations  are  fortui- 
tous ;  in  the  former  the  development  of  tissue-variations 
has  been  in  direct  response  to  the  physical  or  chemical 
influences.  There  are,  however,  in  any  case  fortuitous 
combinations  of  variations. 

Whether  use  and  disuse  are  factors  of  origin  is  also  a 
debatable  point.  Those  who  believe  that  physical  influences 


242  Animal  Life  and  Intelligence. 

on  the  body  are  transmissible  believe  also  that  the  effects 
of  use  and  disuse  are  transmissible. 

The  vital  vigour  of  the  organism  is  a  determining  con- 
dition of  importance.  The  vital  vigour  of  males  has 
favoured  the  origin  of  secondary  sexual  characters  ;  that  of 
females,  the  fostering  and  protection  of  young,  and  therefore 
the  development  in  them  of  vital  vigour. 

The  almost  universally  admitted  factor  in  guidance  is 
natural  selection.  But  we  must  be  careful  not  to  use  it 
as  a  mere  formula. 

Whether  sexual  selection  is  also  a  factor  is  still  a  matter 
of  opinion.  Without  it  the  specific  character  and  constancy 
of  secondary  sexual  features  are  at  present  unexplained. 
If  inherited  use  and  disuse  are  admitted  as  factors  in 
origin,  they  must  also  be  admitted  as  important  factors  in 
guidance. 

Questions  of  origin  and  guidance  should,  so  far  as  is 
possible,  be  kept  distinct.  These  terms,  however,  apply  to 
the  origin  and  guidance  of  variations.  In  the  origin  of 
species  guidance  is  a  factor,  no  doubt  a  most  important 
factor.  The  title  of  Darwin's  great  work  was,  therefore, 
perfectly  legitimate.  And  those  who  say  that  natural 
selection  plays  no  part  in  the  origin  of  species  are,  there- 
fore, undoubtedly  in  error. 


243     ) 


CHAPTEE  VII. 

THE    SENSES   OF   ANIMALS. 

IT  is  part  of  the  essential  nature  of  an  animal  to  be  recep- 
tive and  responsive.  The  forces  of  nature  rain  their 
influence  upon  it ;  and  it  reacts  to  their  influence  in  certain 
special  ways.  Other  organisms  surround  it,  compete  with 
it,  contend  with  it,  strive  to  prey  upon  it,  and  occasionally 
lend  it  their  aid.  It  has  to  adjust  itself  to  this  complex 
environment. 

There  are  two  kinds  of  organic  response — one  more  or 
less  permanent,  the  other  temporary  and  transient.  We 
have  already  seen  something  of  the  former,  by  which  the 
tissues  (the  epidermis  of  the  oarsman's  hand,  and  the 
muscles  of  his  arm)  respond  to  the  call  made  upon  them. 
The  response  is  here  gradual,  and  the  effects  on  the 
organism  more  or  less  enduring.  This,  however,  is  not 
the  kind  of  response  with  which  we  have  now  to  deal. 
What  we  have  now  to  consider  is  that  rapid  response, 
transient,  but  of  the  utmost  importance,  by  means  of  which 
the  organism  directly  answers  to  certain  changes  in  the 
environment  by  the  performance  of  certain  activities.  The 
parts  specially  set  aside  and  adapted  to  receive  special 
modes  of  influence  of  the  environment  are  the  sense- 
organs.  We  human  folk  get  so  much  pleasure  from  and 
through  the  employment  of  our  sense-organs,  that  it  is 
important  to  remember  that  the  primary  object  of  the 
process  of  reception  of  the  influences  from  without  was  not 
the  aesthetic  one  of  ministering  to  the  enjoyment  of  life  by 
the  recipient  organism,  but  the  essentially  practical  one  of 
enabling  that  organism  to  respond  to  these  influences.  In 


244  Animal  Life  and  Intelligence. 

other  words,  the  raison  d'etre  of  the  sense-organs  is  to  set 
agoing  suitable  activities — activities  in  due  response  to 
the  special  stimuli. 

In  this  chapter  we  shall  consider  the  modes  in  which 
the  special  sense-organs  are  fitted  to  receive  the  influences 
of  the  environment,  deferring  to  a  'future  chapter  the  con- 
sideration of  the  resulting  activities.  For  the  present  we 
take  these  activities  for  granted,  observing  them  only  in  so 
far  as  they  give  us  a  clue  to  the  sense-reaction  by  which 
they  are  originated.  In  this  chapter,  too,  we  shall  deal, 
for  the  most  part,  with  the  physiological  aspects  of  sensa- 
tion. In  all  other  organisms  than  ourselves,  that  is  to  say, 
than  each  one  of  us  individually  for  himself,  the  psycho- 
logical accompaniments  of  the  physiological  reactions  of 
the  sense-organs  are  matters  of  inference.  Still,  so  closely 
and  intimately  associated  are  the  physiological  and  the 
psychological  aspects,  that  the  exclusion  of  all  reference  to 
the  latter  would  be  impracticable,  or,  if  practicable,  unad- 
visable.  What  is  practicable  and  advisable  is  to  remember 
that,  even  if  the  two  are  mentioned  in  a  breath,  the  physio- 
logical and  the  psychological  belong  to  distinct  orders  of 
being. 

In  addition  to  the  time-honoured  "five  senses,"  there 
are  certain  organic  sensations,  so  called,  which  take  their 
origin  within  the  body.  These  are,  for  the  most  part, 
somewhat  vague  and  indefinite.  They  do  not  arise  imme- 
diately and  in  direct  response  to  changes  in  the  environ- 
ment, but  indicate  conditions  of  the  internal  organs.  Such 
are  hunger,  thirst,  nausea,  fatigue,  and  various  forms  of 
discomfort.  Although  they  are  of  vital  importance  to  the 
organism,  prompting  it  to  perform  certain  actions  or  to 
desist  from  others,  they  need  not  detain  us  here. 

More  definite  than  these,  but  still  of  internal  origin,  is 
the  muscular  sense.  This,  too,  is  of  continual  service  to 
every  active  animal.  By  it  information  is  given  as  to  the 
energy  of  contraction  of  the  muscles,  and  of  the  amount  of 


The  Senses  of  Animals.  245 

movement  effected — not  to  mention  the  rapidity  and  dura- 
tion of  the  muscular  effort.  By  it  the  position,  or  changes 
of  position,  of  the  motor-organs  are  indicated.  It  is 
obvious,  therefore,  that  the  sensations  obtained  in  this  way, 
some  of  which  are  exceedingly  delicate,  are  an  important 
guide  to  the  organism  in  the  putting  forth  of  its  activities. 
It  is  through  the  muscular  sense  that  we  maintain  an 
upright  position.  It  is  through  an  educated  and  refined 
muscular  sense  that  the  juggler  and  the  acrobat  can 
perform  their  often  surprising  feats.  Concerning  the 
physiology  of  the  muscular  sense,  we  have  at  present  no 
very  definite  knowledge.  Some  have  held  that  we  judge  of 
muscular  movements  by  the  amount  of  effort  required  to 
initiate  them ;  but  it  is  much  more  probable  that  there  are 
special  sensory  nerves,  whose  terminations  are  either  in 
the  muscles  themselves  or  in  the  membranes  which  sur- 
round them. 

We  come  now  to  the  special  senses.  Of  these  we  will 
take  first  the  sense  of  touch.  Through  this  sense  we  are 
made  aware  of  bodies  solid  or  liquid  (or  perhaps  gaseous) 
which  are  actually  in  contact  with  the  skin  or  its  infold- 
ings  at  the  mouth,  nostrils,  etc.  There  are  considerable 
differences  in  the  sensitiveness  of  the  skin  in  different  parts 
of  its  surface ;  some  parts,  like  the  filmy  membrane  which 
covers  the  eye,  being  very  sensitive,  while  others,  like  the 
horny  skin  that  covers  the  heel  of  a  man  who  is  accustomed 
to  much  walking,  are  relatively  callous.  Different  from 
this  is  the  delicacy  of  the  sense  of  touch.  This  delicacy  is 
really  the  power  of  discrimination,  and  therefore  involves 
some  mental  activity.  But  it  is  also  dependent  upon  the 
distribution  of  the  recipient  end-organs  of  the  nerve.  The 
highest  pitch  of  delicacy  is  reached  in  the  tip  of  the  tongue, 
which  is  about  sixty  times  as  delicate  as  the  skin  of  the 
back.  The  power  of  discrimination  is  tested  in  the  follow- 
ing way :  The  points  of  a  pair  of  compasses  are  blunted, 
and  with  them  the  skin  is  lightly  touched.  When  the 
points  are  close  together,  the  sensation  is  of  one  object; 


246  Animal  Life  and  Intelligence. 

when  they  are  more  divergent,  each  point  is  felt  as  distinct 
from  the  other.  On  the  thigh  and  in  the  middle  of  the 
back,  two  distinct  points  of  contact  are  not  felt  unless  the 
compass-tips  are  about  2J  inches  (67'7  millimetres)  apart. 
When  the  divergence  is  2  inches,  they  are  felt  as  one. 
With  the  tip  of  the  tongue,  however,  we  can  distinguish  the 
two  separate  points  when  they  are  only  ^  of  an  inch  (1*1 
millimetre)  apart.  For  the  finger-tip  the  distance  is 
about  ^  of  an  inch  (2  millimetres)  ;  for  the  tip  of  the  nose, 
about  |  of  an  inch  (6 '8  millimetres) ;  for  the  forehead,  a 
little  less  than  an  inch  (22'6  millimetres) ;  and  so  on. 
Shut  your  eyes,  and  allow  a  friend  to  draw  the  compass 
with  the  points  about  £  an  inch  apart,  from  the  forehead 
to  the  tip  of  your  nose,  or  (setting  the  points  about  £  of  an 
inch  apart)  from  the  ball  of  your  thumb  to  the  finger-tip. 
The  increasing  delicacy  and  power  of  discrimination  is 
readily  felt,  and  it  is  difficult  to  believe  that  the  compasses 
are  not  being  slowly  opened. 

It  is  beyond  the  purpose  of  this  chapter  to  describe 
minutely  the  nature  and  structure  of  the  nerve-ends  in 
the  sense-organs.  This  is  a  matter  of  minute  anatomy,  or 
histology.  A  full  description  of  them  as  they  occur  in 
man  will  be  found  in  any  standard  text-book  of  physiology ; 
while  Sir  John  Lubbock's  "  Senses  of  Animals "  gives 
much  information  concerning,  and  many  illustrations  of, 
the  minute  structure  of  the  sense-organs  in  the  inverte- 
brates. Here  I  can  only  touch  very  briefly  on  some  of  the 
more  important  points. 

One  of  the  larger  nerves  of  the  body  (e.g.  the  sciatic 
nerve),  consists  of  a  bundle  of  nerve-threads  collected  from 
a  considerable  area  ;  some  of  these  (motor  threads)  end  in 
muscles,  others  (sensory  threads)  in  the  skin  or  its  neigh- 
bourhood. Each  nerve-thread  has  a  central  axis-fibre, 
which  is  surrounded  by  a  fatty,  insulating  medullary  sheath, 
and  this  by  a  delicate  primitive  sheath.  In  some  parts 
of  the  skin  the  sensory  nerve-threads  lose  their  medullary 
sheath,  and  end  in  very  fine  branches  between  the  cells  of 
the  tissue.  In  other  cases  the  cells  near  their  termination 


The  Senses  of  Animals. 


247 


are  specially  modified  to  form  tactile  cells,  or  tactile 
corpuscles,  in  contact  with  or  surrounding  the  axis-fibre  or 
its  expansion  (Fig.  23). 

Hairs  are  delicate  organs  of  touch,  though,  of  course, 


Fig.  23.— Tactile  corpuscles. 
1.  In  the  beak  of  a  goose.    2.  In  the  finger  of  a  man.    3.  In  the  mesentery  of  a  cat. 

this  is  not  their  only  function.  They  act  as  little  levers 
embedded  in  the  skin. 

Turning  now  to  the  vertebrate  animals  other  than 
man,  we  find  in  them  a  sense  of  touch  closely  analogous 
to  our  own.  As  in  us,  so  in  them,  'the  specially  mobile 
parts  are  eminently  sensitive  and  delicate;  for  instance, 
the  lips  in  many  animals,  such  as  the  horse,  and  the  finger- 
like  organ  at  the  end  of  the  elephant's  trunk.  In  some  of 
them  special  hairs  are  largely  developed  as  organs  of  touch, 
as  in  the  whiskers  of  the  cat  and  the  long  hairs  on  the 
rabbit's  lip.  With  the  aid  of  these  the  rabbit  finds  its  way 
in  the  darkness  of  its  burrow ;  and  it  is  said  that,  deprived 
of  these  organs,  the  poor  animal  blunders  about,  and  is 
unable  to  steer  its  course  in  the  dark. 

The  wing  of  the  bat  is  very  sensitive  to  touch ;  and  it 
is  supposed  that  it  is  through  this  sense  that  the  bat  is 
able  to  direct  its  course  in  the  darkness  of  caves.  Miss 
Caroline  Bolton  thus  describes  an  experimental  trial  of 
this  power  of  the  bat  at  which  she  was  herself  present. 
A  room,  about  twenty  feet  by  sixteen,  was  arranged  with 
strings  crossing  each  other  in  all  directions  so  as  to  form  a 
network  with  about  sixteen  inches  space  between  the  strands. 
To  each  string  was  attached  a  bell  in  such  a  way  that  the 
slightest  touch  would  make  it  ring.  One  corner  of  the  room 


248  Animal  Life  and  Intelligence. 

was  left  free  for  those  who  were  present  at  the  experiment. 
A  bat,  measuring  about  one  foot  from  the  tip  of  one  wing 
to  that  of  the  other,  was  let  loose  in  the  room  when  it  was 
quite  dark,  "  and  it  was  distinctly  heard  flying  about  all 
over  the  room,  but  never  once  did  it  touch  a  string  or  stop 
flying.  It  several  times  came  quite  near  to  the  spectators, 
so  that  they  could  feel  the  vibration  of  the  air  in  their  faces. 
The  experiment  was  continued  for  half  an  hour.  Then, 
when  the  door  was  opened  and  light  let  in,  the  bat  stopped 
flying,  and  settled  down  in  the  darkest  corner."  Now, 
here  it  may  be  said  that,  although  the  room  was  dark  to 
human  spectators,  there  may  have  been  light  enough  for 
a  bat  to  see  his  way.  The  cruel  experiments  of  Spalanzani, 
however,  who  put  out  the  eyes  of  bats  and  obtained  a 
similar  result,  seem  to  show  that  the  animal  is  guided  by 
some  sense  other  than  that  of  sight. 

The  crustaceans  and  many  insects  are  covered  with  a 
dense  armour,  and  it  might  be  supposed  that  in  them 
there  could  be  no  sense  of  touch.    But  this  sense  is  by 
no   means   absent.      Seated  on  the 
tough  integument  are  delicate  little 
hairs,  to  the  base  of  which  a  nerve- 
fibril  passes  through  a  perforation  in 
the  integument.     These  are  specially 
numerous  in  the  antennae  of  insects. 
In  yet  lower  organisms  we  know 
in  some  cases  the  manner  in  which 
°f  they  are  sensitive  to  touch;  but  in 
<JL,  touchr;'™,  cnticie;   a  great  number  of  cases,  although 
observation  shows  that  they  are  thus 
sensitive,  we  know  nothing  definite 
3$i  'STiSmySS,   as  to  how  the   surface  is   specially 
fitted  to  receive  the  stimuli.    Even 

the  primitive  amoeba,  however,  is  sensitive  in  the  sense 
spoken  of  on  p.  8 ;  that  is  to  say,  it  reacts  under  the 
influence  of  a  stimulus. 

Closely  associated  with  the   sense   of   touch    is    the 


The  Senses  of  Animals.  249 

temperature-sense.  Goldschneider  and  others  have  shown 
that  on  the  skin  of  the  human  hand,  for  example,  there  are 
special  points  that  are  sensitive  to  heat  and  cold.  Some 
of  these  little  specialized  areas  are  sensitive  to  cold; 
others  are  sensitive  to  heat ;  and  neither  of  these  seem  to 
be  sensitive  to  pressure.  It  therefore  seems  probable  that 
special  nerve-fibrils  are  set  apart  for  the  temperature- 
sense  ;  but  of  the  manner  in  which  these  fibrils  terminate 
little  or  nothing  is  known. 

Let  us  note  that  this  temperature-sense,  unlike  the 
sense  of  touch,  may  make  us  aware  of  distant  bodies.  It 
is,  tl^n,  what  we  may  term  a  tekesthetic  sense  in  contra- 
distinction to  a  contact-sense.  It  is  stimulated  by  a 
molecular  throb;  the  throbbing  body  may  be  in  contact, 
but  it  may  be  as  distant  as  the  sun,  in  which  case  the 
molecular  pulsations  are  brought  to  us  on  waves  of  sether. 
Whether  these  waves  act  directly  on  the  nerve  end-organs, 
or  indirectly  on  them  through  the  warming  of  the  skin- 
surface  in  which  they  terminate,  we  cannot  say  for  certain. 
But  if  the  hand  be  held  before  a  heated  stove  and  be 
sheltered  from  the  heat  by  a  screen,  the  removal  of  the 
screen,  even  for  the  fraction  of  a  second,  gives  rise  to  a 
strong  stimulation  of  the  temperature-sense,  though  the 
skin-surface  be  not  appreciably  raised  in  temperature. 
Hence  it  is  probable  that  the  end-organs  are  stimulated 
directly,  and  not  indirectly. 

Concerning  the  temperature-sense  in  the  lower  animals, 
nothing  definite  is  known.  But  it  is  impossible  to  see  our 
familiar  pets  basking  in  the  sunshine,  or  a  butterfly  sunning 
itself  on  a  bright  summer's  day,  without  feeling  confident 
that  the  temperature-sense  is  a  channel  of  keen  enjoy- 
ment. As  before  mentioned,  however,  this  is  not  to  be 
regarded  as  the  primary  end  in  sensation.  The  primary 
end  is  not  life-enjoyment,  but  life-preservation.  And  we 
must  regard  the  temperature-sense  as  developed  in  the 
first  instance  to  enable  the  organism  to  escape  from  the 
ill  effects  of  deleterious  heat  or  cold,  and  to  seek  those 
temperature -conditions  which  are  most  helpful  to  the 


250  Animal  Life  and  Intelligence. 

continued  and  healthful  fulfilment  of  the  process  of 
life. 

The  sense  of  taste  is  called  into  play  by  certain  soluble 
substances,  or  liquids,  which  must  come  in  contact  with 
the  specialized  nerve-endings.  Under  normal  circum- 
stances, the  sense  of  taste  is  closely  associated  with  that 
of  smell,  the  result  of  the  combination  of  the  two  special 
senses  being  a  flavour.  The  bouquet  of  a  choice  wine,  the 
flavour  of  a  peach,  involve  both  senses ;  quinine  involves 
taste  alone ;  and  garlic  and  vanilla  are  nearly,  if  not  quite, 
tasteless, — what  we  call  their  taste  is  in  reality  their  action 
on  the  organ  of  smell. 

It  is  difficult  to  classify  tastes.  Sweet,  bitter,  salt, 
alkaline,  sour,  acid,  astringent,  acrid, — these  are  the  pro- 
minent and  characteristic  varieties. 

This  sense  is  generally  localized  in  or  near  the  mouth  ; 
in  us  mainly  in  the  tongue.  One  manner,  but  not  the  only 
manner,  in  which  the  nerves  in  this  region  terminate  is 
in  the  minute  flask-shaped  taste-buds,  which  have  near 
one  end,  where  they  reach  the  surface,  a  funnel-shaped 
opening,  the  taste-pore.  They  are  made  up  of  elongated 
cells,  some  of  which  near  the  centre 
are  spindle-shaped,  and  are  called 
taste-cells.  They  are  found  chiefly 
round  the  large  circumvallate  papillae ; 
but  in  the  rabbit  and  some  other 
animals  they  are  collected  in  the 
folds  of  a  little  ridged  or  pleated  patch 
—the  papitta  foliata— on  each  side 
section  across  part  of  the  of  the  tongue  near  the  cheek-teeth. 
ta8te-budsafarther  eniargei  * '  It  is  probable  that  the  stimulation 

of  the  end-organs  of  taste  is  effected  by  the  special  mode  of 
molecular  vibration  due  to  the  chemical  nature  of  the 
sapid  substance.  Mr.  J.  B.  Haycroft,  in  a  paper  read 
before  the  Koyal  Society  of  Edinburgh,*  suggests  that  "  a 
group  of  salts  of  similar  chemical  properties  have  their 

*  See  abstract  in  Nature,  vol.  xxxiv.  p.  515. 


The  Senses  of  Animals.  251 

molecules  in  a  similar  vibrating  condition,  giving  rise  to 
similar  colours  and  similar  tastes."  "  Thus  the  chlorides 
and  sulphates  of  a  series  of  similar  elements — called  a 
group  of  elements  by  Mendeljeff — have  similar  tastes." 

The  delicacy  of  the  sense  of  taste  in  man  has  been  the 
subject  of  investigation  by  Messrs.  E.  H.  S.  Bailey  and 
E.  L.  Nichols.*  They  give  the  following  table  : — 

L  Quinine — 

Male  observers  detected  1  part  in  390,000  parts  of  water. 
Female       „  „        1       „       456,000       „ 

II.  Cane-sugar — 

Male  observers        „        1       „  199      „          „ 

Female       „  „        1       „  204      „          „ 

III.  Sulphuric  acid- 

Male  observers        „        1       „  2,080      „          „ 

Female       „  „        1       „  3,280      „ 

IV.  Bicarbonate  of  sodium — 

Male  observers  „        1       „  98      „          „ 

Female        „  „         1       „  126       „          „ 

V.  Common  salt — 

Male  observers  „        1       „  2,240      „ 

Female  1 


The  above  figures  represent  means  or  averages  of  a 
great  number  of  individuals.  There  was  very  considerable 
variation  for  some  tastes.  In  the  case  of  the  bitter  of 
quinine,  the  maximum  delicacy  was  the  detection  of  1  part 
in  5,120,000  parts  of  water;  the  minimum  1  part  in 
456,000  parts  of  water.  Except  in  the  case  of  salt,  the 
sense  was  more  delicate  in  women  than  in  men.  It  is  not 
stated  whether  the  men  tested  were  smokers. 

It  does  not  seem  necessary  to  say  anything  concerning 
the  sense  of  taste  in  the  lower  mammalia. 

In  birds  and  reptiles  the  sense  of  taste  does  not  appear 
to  be  highly  developed.  Parrots  are,  perhaps,  better  off 
in  this  respect  than  the  majority  of  their  class ;  and  the 
ducks  have  special  organs  on  the  edges  of  the  beak,  which 
seem  to  minister  to  this  sense.  A  python  at  the  Zoological 
Gardens,  partially  blind  owing  to  a  change  of  skin,  is  said 
to  have  struck  at  an  animal,  but  to  have  only  succeeded 

*  See  Nature,  vol.  xxxvii.  p.  557. 


252  Animal  Life  and  Intelligence. 

in  capturing  its  blanket.  This,  however,  it  constricted, 
and  proceeded  to  swallow  with  abundant  satisfaction. 

It  may  here  be  mentioned  that  the  scales  and  skua  of 
many  fishes  are  provided  with  sense-organs  which  very 
closely  resemble  the  taste-buds  of  higher  animals.  They 
occur  in  the  head  and  along  the  "  lateral  line  "  which  runs 
down  the  side  of  the  fish,  and  may  be  readily  seen,  for 
example,  in  the  cod.  Mr.  Bateson's  *  careful  observations 
at  Plymouth  gave,  however,  no  indication  of  the  possession 
of  an  olfactory  or  gustatory  function,  and  their  place  in 
the  sensory  economy  of  the  fish  remains  problematical.  In 
or  near  the  mouth  similar  end-organs  are  found  to  be  some- 
what variously  developed  in  different  fishes — on  the  palate 
and  lips,  on  the  gill-bars,  more  rarely  on  the  tongue,  and  on 
the  barbels  of  the  rockling  and  the  pout.  How  far  any  or  all 
of  these  have  a  gustatory  function  remains  to  be  proved. 

Anglers  and  fishermen,  however,  from  their  everyday 
experience,  and  naturalists  from  special  observations,  do 
not  doubt  that  fishes  have  a  sense  of  taste.  Professor 
Herdman's  recent  experiments  on  feeding  fishes  with  nudi- 
branchs  |  (naked  molluscs)  seem  to  show,  for  example,  that 
the  fishes  concerned,  including  shannies,  flat-fish,  cod, 
rockling,  and  others,  have  a  sense  of  taste  leading  them 
to  reject  these  molluscs  as  nasty.  They  show,  too,  that 
some  of  the  nudibranchs  (Doris,  Ancula,  Eolis)  are  pro- 
tected by  warning  coloration. 

Our  knowledge  of  the  sense  of  taste  among  the  lower 
(invertebrate)  animals  is  imperfect,  and  is  largely  based 
rather  on  observation  of  their  habits  than  on  the  evidence 
of  anatomical  structure.  Here,  again,  comes  in  the 
difficulty  of  distinguishing  between  taste  and  smell.  But 
even  if  the  caterpillars  which  refuse  to  eat  all  but  one  or 
two  special  herbs,  or  the  races  of  bloodsuckers  which  seem 
to  have  individual  and  special  tastes,  are  guided  in  part 
by  an  olfactory  sense,  there  is  much  evidence  which  seems 

*  "  Sense-Organs  and  Perception  of  Fishes : "    Journal  of  Marine  Bio- 
logical  Association,  New  Series,  vol.  i.  No.  3,  p.  225. 
t  Nature,  vol.  xlii.  p.  201. 


The  Senses  of  Animals.  253 

to  admit  of  no  alternative  explanation.  Moisten,  for 
example,  the  antennae  of  a  cockroach  with  a  solution  of 
Epsom  salts  or  quinine,  and  watch  him  suck  it  off;  or 
repeat  F.  Will's  experiments  on  bees,  tempting  them  with 
sugar,  and  then  perfidiously  substituting  pounded  alum. 
The  way  in  which  these  little  insects  splutter  and  spit 
suggests  that,  whatever  may  be  the  psychological  effect, 
the  physiological  effect  is  analogous  to  that  produced  in 
us  by  an  exceedingly  nasty  taste.  Here  smell  would  seem 
to  be  excluded.  Forel,  moreover,  mixed  strychnine  with 
honey,  and  offered  it  to  his  ants.  The  smell  of  the  honey 
attracted  them,  but  when  they  began  to  feed,  the  effect  of 
the  taste  was  at  once  evident. 

The  organs  of  taste  in  insects  are  probably  certain 
minute  pits,  in  each  of  which  is  a  delicate  taste-hair, 
which,  in  some  cases,  is  perforated  at  the  free  end.  They 
occur  in  the  maxillae  and  tongue  in  ants  and  bees,  and  on 
the  proboscis  of  the  fly. 

In  many  of  the  invertebrates,  the  crayfish  and  the  earth- 
worm, for  example — to  take  two  instances  from  very  different 
groups — observation  seems  to  show  that  a  sense  of  taste  is 
developed,  for  they  have  marked  and  decided  food-pre- 
ferences. Nevertheless,  the  existence  of  special  organs  for 
this  purpose  has  not  been  definitely  proved. 

The  sense  of  taste  no  doubt  ministers  to  the  enjoyment 
of  life.  But,  presumably,  it  has  been  developed  in  sub- 
servience to  the  process  of  nutrition.  Primarily,  taste  was 
not  an  end  in  itself,  but  was  to  guide  the  organism  in  its 
selection  of  food  that  could  be  assimilated.  Nice  and  nasty 
were  at  first,  and  still  are  to  a  large  extent,  synonymous 
with  good-for-eating  and  not-good-for-eating.  With  un- 
wonted substances,  however,  its  testimony  may  be  false. 
Sugar  of  lead  is  sweet,  but  fatal.  Brought  to  a  new 
country,  cattle  often  eat,  apparently  with  relish,  poisonous 
plants.  Still,  under  normal  circumstances,  the  testimony 
of  taste  is  reliable. 

The  sense  of  smell  is,  to  a  large  extent,  telaesthetic.     It 


254  Animal  Life  and  Intelligence. 

is  true  that  the  stimulation  of  the  end-organs  is  effected  by 
actual  contact  with  the  odoriferous  vapour.  But  since  this 
vapour  may  be  given  off  from  an  odoriferous  body  at  some 
distance  from  the  organism,  such  as  a  flower  or  a  decom- 
posing carcase,  it  is  clear  that  the  sense  gives  information 
of  the  existence  of  such  bodies  before  they  themselves  come 
in  contact  with  us.  Primitively,  we  may  suppose  that  it 
was  developed  in  connection  with  that  sense  of  taste  with 
which,  as  we  have  seen,  it  is  so  closely  associated.  In  this 
respect  smell  is  a  kind  of  anticipatory  taste.  But  it  has 
now  other  ends,  apart  from  those  which  are  purely  aesthetic. 
In  us  it  may  serve  as  a  warning  of  a  pestilential  atmo- 
sphere ;  in  many  organisms,  such  as  the  deer,  it  gives 
warning  of  the  presence  of  enemies ;  in  many  again,  and 
some  insects  among  the  number,  it  is  the  guiding  sense  in 
the  search  for  mates. 

The  organ  of  smell  in  ourselves  and  in  all  the  mammalia 
is  the  delicate  membrane  that  covers  the  turbinal  bones  in 
the  nose.  It  contains  cells  with  a  largish  nucleus,  around 
which  the  protoplasm  is  mainly  collected.  A  filament 
passes  from  this  to  the  surface,  and  ends  in  a  fine  hair  or 
cilium  (or  a  group  of  hairs  or  cilia  in  birds  and  amphibia) ; 
a  second  filament  runs  downwards  into  the  deeper  parts  of 
the  tissue,  and  may  pass  into  a  nerve-fibril. 

In  us  and  air-breathing  creatures,  the  substance  which 
excites  the  sensation  of  smell  must  be  either  gaseous  or  in 
a  very  fine  state  of  division;  but  in  water-breathers  the 
substance  exciting  this  sensation — or,  in  any  case,  one  of 
anticipatory  taste — may  be  in  solution.  The  sensitiveness 
of  the  olfactory  membrane  is  very  remarkable.  A  grain  of 
musk  will  scent  a  room  for  years,  and  yet  have  not  sensibly 
lost  in  weight.  Drs.  Emil  Fischer  and  Penzoldt  found 
that  our  olfactory  nerves  are  capable  of  detecting  the 
*67To~ow  P8-1*  °f  a  milligramme  of  chlorophenol,  and  the 
4^<Joooooo  Par*  °f  a  milligramme,  or  about  one  thirty- 
thousand-millionth  of  a  grain,  of  mercaptan.  It  may  be 
that  to  such  substances  our  olfactory  sensibility  is  especially 
delicate. 


The  Senses  of  Animals.  255 

Not  much  is  known  concerning  the  manner  in  which 
the  end-organs  of  smell  are  stimulated.  As  in  the  case  of 
taste,  it  is  probably  a  matter  of  molecular  vibration ;  and 
Professor  William  Bamsay  has  suggested  that  the  end- 
organs  are  stimulated  by  vibrations  of  a  lower  order  than 
those  which  give  rise  to  sensations  of  light  and  heat.  He 
has  also  drawn  attention  to  the  fact  that  to  produce  a 
sensation  of  smell,  the  substance  must  have  a  molecular 
weight  at  least  fifteen  times  that  of  hydrogen. 

It  is  well  known  that  the  sense  of  smell  is  in  some  of 
the  mammalia  exceedingly  acute.  The  dog  can  track  his 
master  through  a  crowded  thoroughfare.  The  interesting 
experiments  of  Mr.  Eomanes  *  show  that,  under  ordinary 
conditions  of  civilized  life,  the  smell  of  boot-leather  is  a 
factor/and  the  dog  tracks  his  master's  boots.  In  one  case, 
the  boots  were  soaked  in  oil  of  aniseed,  but  this  to  us 
powerful  scent  did  not  overcome  the  normal  odour  of 
the  master's  boots.  Mr.  W.  J.  Eussell,  in  a  subsequent 
number  of  the  same  periodical,  describes  how  his  pug  could 
find  a  small  piece  of  biscuit  by  scent,  and  this  odour  of 
biscuit  was  not  overmastered  by  a  strong  smell  of  eau-de- 
Cologne.  Deer-stalkers  know  well  how  keen  is  the  sense 
of  smell  in  the  antlered  ruminants. 

We  must  not,  however,  be  too  ready  to  conclude,  from 
these  observations,  that  the  olfactory  membrane  is  absolutely 
more  sensitive  in  such  animals  than  it  is  in  man.  It  may 
well  be  that,  though  they  are  so  keen  to  detect  certain 
scents,  they  are  dull  to  those  which  affect  us  power- 
fully. It  is  quite  possible  that  the  odour  of  aniseed  or 
eau-de-Cologne  is — possibly  from  the  fact  that  iheir  end- 
organs  are  not  attuned  to  these  special  molecular  vibrations 
— out  of  their  range  of  smell.  Their  special  interests  in 
life  have  led  to  the  cultivation  of  extreme  sensibility  to 
special  tones  of  olfactory  sensation.  Under  unusual  cir- 
cumstances, man  may  cultivate  unwonted  modes  of  utilizing 
the  sense  of  smell.  A  boy,  James  Mitchell,  who  was  born 
blind,  deaf,  and  dumb,  and  who  was  mainly  dependent  on 

*  Nature,  vol.  xxxvi.  p.  273. 


256  Animal  Life  and  Intelligence. 

the  sense  of  smell  for  keeping  up  some  connection  with  the 
external  world,  observed  the  presence  of  a  stranger  in  the 
room,  and  formed  his  opinion  of  people  from  their  charac- 
teristic smell.  On  the  whole,  therefore,  we  may,  perhaps, 
conclude  that  the  variations  in  sensitiveness  are  mainly 
relative  to  the  needs  of  life. 

In  birds  the  sense  of  smell  is  but  little  developed,  not- 
withstanding all  that  most  interesting  naturalist,  Charles 
Waterton,  wrote  on  the  subject.  Vultures  seem  unable  to 
discover  the  presence  of  food  which  is  hidden  from  their 
sight.  Probably  reptiles  share  with  them  this  dulness  of 
the  sense  of  smell. 

It  has  already  been  remarked  that,  in  the  case  of 
aquatic  animals,  there  is  probably  little  distinction  between 
taste  and  smell.  It  would  be  well,  perhaps,  to  restrict  the 
word  "  smell "  to  the  stimuli  produced  by  vapours  or  air- 
borne 'particles,  and  to  use  the  phrase  "  telaesthetie  taste," 
or  simply  "  taste,"  for  those  cases  where  the  effects  are 
produced  through  the  medium  of  solution.  In  this  case, 
however,  the  point  to  be  specially  noticed  is  that  taste  in 
aquatic  animals  becomes  a  telaesthetic  sense,  informing  the 
organism  of  the  presence  of  more  or  less  distant  food. 
Thus,  if  you  stir  with  your  finger  the  water  in  which 
leeches  are  living,  they  will  soon  flock  to  the  spot,  showing 
that  the  telsesthetic  sense  is  associated  with  an  appreciation 
of  direction.  If  a  stick  be  used  to  stir  the  water,  they  do  not 
take  any  notice  of  it.  Mr.  W.  Bateson  *  has  shown  that 
there  are  many  fishes,  among  which  are  the  dog-fish, 
skate,  conger  eel,  rockling,  loach,  sole,  and  sterlet,  which 
habitually  seek  their  food  by  scent  (telaesthetic  taste),  aided 
to  some  extent  by  touch,  and  but  little,  if  at  all,  by  sight. 
"  None  of  these  fishes  ever  starts  in  quest  of  food  when  it  is 
first  put  into  the  tank,  but  waits  for  an  interval,  doubtless 
until  the  scent  has  been  diffused  through  the  water. 
Having  perceived  the  scent  of  food,  they  swim  vaguely 
about,  and  appear  to  seek  it  by  examining  the  whole  area 
pervaded  by  the  scent,  having  seemingly  no  sense  of  the 

*  Journal  of  Marine  Biological  Association,  New  Series,  vol.  i.  No.  3,  p.  235. 


The  Senses  of  A  nimals.  257 

direction  whence  it  proceeds."  I  venture  to  think  that 
further  observation  and  experiment  may  show  that  such  a 
sense  of  direction  does  in  some  cases  exist.  Some  years 
ago  I  was  fishing  in  Simon's  Bay,  at  the  Cape,  with  a  long 
casting-line.  The  sea  was  unusually  calm,  and  the  water 
clear  as  crystal.  Beneath  me  was  a  clear  patch  of  granite, 
two  or  three  yards  across,  surrounded  by  tangled  seaweed. 
Evening  was  coming  on,  and  I  was  just  going  to  put  up 
my  tackle  when  I  saw  a  long  dark  fish  slowly  sail  into  the 
open  space  and  take  up  his  position  at  one  side.  My  line 
was  out,  baited,  I  think,  with  a  piece  of  cuttle-fish,  and  I 
tried  to  draw  it  into  the  clear  space,  but  only  succeeded 
in  bringing  it  to  within  a  foot  or  so  of  the  side  furthest 
from  the  fish.  There  it  got  hitched  in  the  weed ;  but  the 
fish  being  still  undisturbed,  I  awaited  further  developments. 
After  two  or  three  minutes  the  fish  slowly  turned,  crossed 
the  pool,  and  remained  motionless  for  a  few  moments  ; 
then  he  proceeded  straight  to  the  bait ;  and  in  a  few 
minutes  I  had  landed  a  dog-fish  between  four  and  five  feet 
long.  I  did  not  then  know  that  the  dog-fish  sought  its 
food  mainly  or  solely  by  scent  (taste) ;  but  in  any  case  I  do 
not  think  in  this  instance  he  could  have  seen  the  bait, 
hidden  as  it  was  amid  the  seaweed. 

Although  I  am  aware,  and  have  already  mentioned, 
that  Mr.  Bateson's  observations  do  not  support  the  view 
that  the  sense-organs  of  the  lateral  line  minister  to  this 
telsesthetic  sense,  still  I  think  that  further  observations 
and  experiments  may  show  that  these  sense-organs  are 
"  olfactory,"  and  that  the  lateral  development  may  be  in 
relation  to  the  appreciation  of  the  direction  in  which  the 
food  lies.  It  is,  however,  a  difficult  matter  to  determine, 
and  the  few  experiments  I  have  made  are  so  far  incon- 
clusive. 

Much  has  been  written  concerning  the  sense  of  smell  in 
insects.  That  they  possess  such  a  sense  few  will  be  dis- 
posed to  doubt.  The  classical  observations  of  Huber  show 
that  bees  are  affected  by  the  smell  of  honey,  and  that  the 
penetrating  odour  of  fresh  bee-poison  will  throw  a  whole 


258  Animal  Life  and  Intelligence. 

hive  into  a  state  of  commotion.  He  was  of  opinion  that 
the  impunity  with  which  his  assistant,  Francis  Burnens, 
performed  his  various  operations  on  bees  was  due  to  the 
gentleness  of  his  motions,  and  the  habit  of  repressing  his 
respiration,  it  being  the  odour  transmitted  by  the  breath  to 
which  the  bees  objected.  Sir  John  Lubbock  formed  a  little 
bridge  of  paper,  and  suspended  over  it  a  camel's-hair  brush 
containing  scent,  and  then  put  an  ant  at  one  end.  She 
ran  forward,  but  stopped  dead  short  when  she  came  to  the 
scented  brush.  Dr.  McCook  introduced  a  pellet  of  blotting- 
paper  saturated  with  eau-de-Cologne  into  the  neighbour- 
hood of  some  pavement-ants,  who  were  engaged  in  a  free 
fight.  The  effect  was  instantaneous  ;  in  a  very  few  seconds 
the  warriors  had  unclasped  mandibles,  relaxed  their  hold 
of  their  enemies'  legs,  antennae,  or  bodies. 

The  correct  localization  of  the  sense  of  smell  has  been 
a  matter  of  difficulty.  Kirby  and  Spence  localized  it  at 
the  extremity  of  the  "  nose,"  between  it  and  the  upper  lip. 
That  the  nose,  they  naively  remark,  corresponds  with  the 
so-named  part  in  mammalia,  both  from  its  situation  and 
often  from  its  form,  must  be  evident  to  every  one  who  looks 
at  an  insect.  Lehman,  Cuvier,  and  others,  misled  by  the 
fact  that  the  organ  of  smell  is  in  us  localized  at  the 
entrance  of  the  air-track,  supposed  that  at  or  near  the 
spiracles  of  insects  were  the  organs  of  smell.  Modern 
research  tends  more  and  more  clearly  to  localize  the  sense 
of  smell,  as  first  suggested  by  Eeaumur,  in  the  feelers  or 
antennae,  and  in  some  cases  also  in  the  palps.  If  the 
antennae  of  a  cockroach  be  extirpated  or  coated  with 
paraffin,  he  no  longer  rushes  to  food,  and  takes  little  notice 
of,  and  will  sometimes  even  walk  over,  blotting-paper 
moistened  with  turpentine  or  benzoline,  which  a  normal 
insect  cannot  approach  without  agitation.  There  can  be 
little  doubt  that  it  is  by  means  of  its  large  branching 
antennae  that  the  male  emperor  moth  (Saturnia  carpini)  is 
able  to  find  its  mate.*  If  a  collector  take  a  virgin  female 

*  Mr.  S.  Klein  mentions  a  similar  fact  in  connection  with  Bombyx  quercus 
(Xature,  voL  xxxv.  p.  282). 


The  Senses  of  Animals. 


259 


into  a  locality  frequented  by  these  moths,  he  will  soon  be 
surrounded  by  twenty  or  thirty  males;  but  if  the  moth 
be  not  a  virgin,  he  will  at  most  see  one  or  two  males. 
The  sense  of  smell  is  thus  delicate  enough  to  distinguish 
the  fertilized  from  the  unfertilized  female,  and  has  asso- 
ciated with  it  a  sense  of  direction  by  which  the  insect  is 
guided  to  the  right  spot.  Carrion  flies  whose  antennas 
have  been  removed  fail  to  discover  putrid  flesh;  and  E. 
Hasse  has  observed  that  male  humble-bees  whose  antennae 
have  been  removed  cannot  discover  the  females.  The 
sensory  elements  are  lodged  in  pits  or  cones,  which  may  be 
filled  with  liquid,  peculiar  sensory  rods  or  hairs  being 
associated  with  the  nerve-end- 
ings. Of  these  pits  the  queen- 
bee  has,  according  to  Mr. 
Cheshire,  1600,  the  worker  2400, 
and  the  drone  nearly  19,000,  on 
each  antennae.  On  the  antennae 
of  the  male  cockchafer,  Hauser 
estimates  the  number  to  be 
39,000. 

In  the  aquatic  crayfish  there 
are,  besides  the  long  antennas, 
smaller  antennules,  each  of 
which  has  two  filaments,  an 
inner  and  an  outer.  On  the 
under  surface  of  most  of  the 
joints  of  the  outer  filament 
there  are  two  bunches  of 
minute,  curiously  flattened  or- 
gans, which  were  regarded  by  Fig'  26-Antennule  otoayflah. 

?        ,.  ,,      .          ,.         6  '       J      *J-  inner  joint;   o.j.,  outer  joint;    ol., 

.Leyd.lg,       their       diSCOVerer         as  olfactory  set*;    ol'.,  the  same,  enlarged; 

/       &  °  au,op.,  auditory  opening  in  the  basal  di- 

oliactory.       Observation,     too  vision>  which  has  been  cut  °Pen  to  show 

'  au.s.,  the  auditory  sac;    au.n.,   auditory 

seems  to  confirm  the  view  that  nervebranchiDgtothetworidge8besetwith 

aal  auditory  hairs;    au.h.,  auditory  hair,  en- 

the   sense  of  smell   (or  telaas-  larsed-  (After  Howes.) 
thetic  taste)  is  located  in  the   antennule.     I  tried  on  a 
crayfish  the  following  experiment:  When  it  was  at  rest 
at  the  bottom  of  its  tank,   I  allowed  a  current  of  pure 


260  Animal  Life  and  Intelligence. 

water  (the  water  in  which  it  lived)  to  flow  from  a  pipette 
over  its  antennas  and  antennules.  The  antennae  moved 
slowly,  but  the  antennules  remained  motionless.  I  then 
took  some  water  in  which  a  cod's  head  had  been  boiled, 
and  allowed  some  of  this  to  stream  over  the  antennas  and 
antennules.  The  former  moved  slightly  as  before,  but  the 
antennules  were  thrown  into  a  rapid  up-and-down  jerky 
vibration,  and  shortly  afterwards  the  crayfish  began  moving 
about  the  bottom  of  its  tank.  If  only  one  antennule  be 
thus  stimulated,  or  stimulated  to  a  higher  degree  than  the 
other,  the  crayfish  seems  generally  (but  not  always)  to 
turn  to  that  side  in  search  of  food.  Mr.  Bateson  *  has 
shown  to  how  large  an  extent  shrimps  and  prawns  seek  their 
food  by  smell,  and  states  that  a  prawn,  though  blind,  will 
often  find  his  way  back  to  his  proper  place,  and  stay  in  it. 
In  the  snail  the  anterior  pair  of  "  horns,"  or  tentacles, 
are  said  to  be  olfactory.  Near  the  end  of  each  is  a  large 
ganglion,  or  nerve-knot,  from  which  fibres  pass  to  the 
surface,  in  which  there  are  said  to  be  developed  sensory 
knobs.  Snails,  however,  from  which  these  tentacles  have 
been  removed  are  apparently  still  possessed  of  a  sense  of 
smell.  Certain  lobed  processes  round  the  mouth  have 
been  regarded  as  the  seat  of  olfactory  sensation,  but  this 
is  doubtful.  In  the  foot  of  the  snail,  the  part  on  which 
it  glides,  there  is  a  hollow  gland,  and  in  this  there  are 
special  cells,  each  of  which  gives  off  a  delicate  rod,  en- 
larging at  the  free  end  into  a  ciliated  knob.  These  are 
regarded  as  sensory  and,  it  may  be,  olfactory.  In  shell- 
fish like  the  mussel,  in  which  the  water  is  sucked  in  by 
an  inhalent  tube  or  siphon,  and  ejected  through  an  ex- 
halent  siphon  above  it  (see  Fig.  2,  p.  4),  there  is  at  the 
entrance  of  the  incoming  current  a  thin  layer  of  elongated 
cells  which  are  described  as  olfactory,  and  are  in  association 
with  a  special  ganglion.  Olfactory  depressions  have  been 
described  in  some  worms.  But  in  a  great  number  of  the 
lower  invertebrates  very  little  or  nothing  is  known  concern- 
ing a  sense  of  smell. 

*  Journal  of  Marine  Biological  Association,  New  Series,  vol.  i.  No.  2,  p.  211. 


* 


')   i' 
The  Senses  of  Animals.  261 


Hearing  is  a  telassthetic  sense.  Through  it  we  become 
aware  of  certain  vibratory  states  of  more  or  less  distant 
objects.  The  vibrations  of  these  bodies  are  transferred  to 
the  air  or  other  medium  surrounding  the  body,  and  are 
transmitted  through  the  air  or  other  medium  to  the  ear. 
The  sound-waves  traverse  the  air  at  a  rate  of  337  metres 
(1106  feet)  in  a  second ;  but  they  travel  about  four  times 
as  fast  in  water.  If  the  vibration  is  periodic  or  regular, 
the  sound  is  called  a  tone ;  non-periodic  or  irregular  sounds 
are  noises.  The  pitch  of  a  tone  is  determined  by  the 
number  of  vibrations  in  a  second.  The  lowest  or  gravest 
tone  most  of  us  can  hear  is  that  where  there  are  about  30 
vibrations  in  a  second ;  twice  this  number  give  us  a  tone 
of  an  octave  higher  ;  twice  this  again,  another  octave ;  and 
so  on.  In  musical  composition,  tones  from  about  40  to 
about  4000  vibrations  per  second  are  employed.  This  is 
a  range  of  somewhat  over  six  octaves.  But  many  of  us 
are  capable  of  hearing  sounds  over  a  range  of  about  ten 
octaves,  that  is  to  say,  from  30  to  30,000  vibrations  per 
second.  The  upper  limit  of  hearing  is,  however,  very 
variable.  Some  people  are  deaf  to  tones  of  more  than 
15,000  or  20,000  vibrations  per  second.*  Others  may  hear 
shrill  tones  of  40,000,  or  even  in  rare  cases  50,000.  I 
could  as  a  boy  hear  the  shrill  squeak  of  a  bat ;  now  I  am 
quite  deaf  to  it.  A  friend  of  mine  in  South  Africa  was 
unable  to  hear  the  piping  of  the  frogs  in  the  pond,  which 
was  to  me  so  loud  as  almost  to  drown  the  tones  of  his 
voice. 

Apart  from  the  pitch  of  a  note  is  its  quality.  The 
same  note  struck  on  different  instruments  or  sung  by 
different  persons  has  a  different  ring.  This  is  determined 
by  the  number  and  intensity  of  overtones,  or  partials,  which 
are  associated  with  the  fundamental  tone.  Suppose  the 
deep  fundamental  tone  of  33  vibrations  be  sounded ;  with  it 
there  may  be  associated  overtones,  eight  or  nine  in  number, 
all  of  which  are  simple  multiples  (twice,  thrice,  four  times, 

*  A  friend  of  mine  informs  me  that  his  limit  is  about  17,500  per  second, 
20,000  being  quite  inaudible. 


262  Animal  Life  and  Intelligence. 

and  so  on)  of  the  fundamental  33.  The  effects  of  these 
on  the  organ  of  hearing  fuse  or  combine  with  the  pre- 
dominant effect  of  the  fundamental  tone.  In  harmonious 
chords,  also,  two  or  more  fundamental  tones,  with  their 
accompaniment  of  partials,  blend  in  sensation  so  com- 
pletely that  it  requires  a  keen  musical  ear  and  some 
training  to  analyze  them  into  their  component  elements. 

The  delicacy  of  discrimination  of  tones  is  greatest  in 
the  mid-region  of  hearing  ;  and  there  is  much  individual 
variation  in  accuracy  of  ear.  I  have  made  experiments  on 
many  individuals  to  test  their  powers  in  this  respect.  I 
found  some  who  were  unable,  in  the  mid-region  of  hearing, 
to  state  which  was  the  higher  of  two  notes  sounded  on  a 
violin,  the  tones  of  which  were  separated  by  a  major  third, 
and  in  one  case  by  a  fifth.  With  notes  on  the  piano  the 
discrimination  was  more  delicate,  and  yet  more  delicate 
when  the  notes  were  sung.  In  such  cases  tone-discrimina- 
tion is  deficient ;  and  between  these  and  the  musician,  who 
is  stated  to  be  able  to  distinguish  tones  separated  by  only 
6*f  of  a  tone,  there  are  many  intermediate  stages. 

It  is  beyond  my  purpose  to  describe,  in  more  than  a 
very  general  way,  the  nature  of  the  auditory  apparatus  of 
man.  The  vibrations  of  the  air  are  received  by  the  drum- 
membrane,  which  lies  in  the  auditory  passage.  From  this 
it  is  transmitted,  by  a  chain  of  small  bones,  to  the  inner 
auditory  apparatus.  This  consists  of  two  small  mem- 
branous sacs,  with  one  of  which  three  membranous  looped 
tubes,  the  semicircular  canals,  are  connected;  with  the 
other  is  connected  a  spiral  tube,  the  cochlear  canal.  These 
membranous  sacs  and  canals  are  filled  with  fluid,  and  are 
surrounded  by  the  fluid  which  fills  the  bony  cavity  in 
which  they  lie.  This  bony  cavity  has  two  little  windows, 
one  oval  and  the  other  round,  across  each  of  which  a 
membrane  is  stretched.  The  oval  membrane  is  in  con- 
nection with  the  chain  of  auditory  bones ;  and  when  this 
is  made  to  vibrate  in  and  out,  the  membrane  of  the  round 
window  vibrates  out  and  in.  Thus  the  fluid  around  and 
within  the  membranous  sacs  and  canals  is  set  in  vibration. 


The  Senses  of  Animals.  263 

And  the  parts  are  so  arranged  that  the  vibrations,  in 
passing  from  the  oval  to  the  round  membrane/' must  run 
up  one  side  and  down  the  other  side  of  the  cochlear  canal. 
As  they  run  down  they  set  in  vibration  a  delicate  mem- 
brane which  is  supported  on  beautiful  arched  rods  (the 


c.  c 


Fig.  27.— Diagram  of  ear. 

t.m.,  tympanic  membrane,  to  which  is  attached  a  chain  of  small  bones  stretching  across 
the  cavity  of  the  drum,  the  innermost  of  which,  St.,  fits  into  the  "  oval  window."  The  vibra- 
tions are  transmitted  up  one  side  and  down  the  other  side  of  the  cochlear  canal,  c.c.,  and  thus 
reach  the  "  round  window,"  f.r. ;  s.c.  is  one  of  the  semicircular  canals,  the  other  two  are 
omitted ;  e.t.  is  the  Eustachian  tube  connecting  the  cavity  of  the  drum  with  the  mouth-cavity. 

organs  of  Corti).  And  this  membrane  contains  a  number 
of  special  hair-cells,  so  called  because  they  bear  minute 
hair-like  structures.  These  are  the  special  end-organs  of 
hearing.  It  has  been  suggested  that  the  fibres  of  the 
membrane  on  the  arched  rods,  which  are  of  different 
lengths  and  may  be  stretched  with  differing  degrees  of 
tension,  respond  to  vibrations  of  different  pitch.  Thus  the 
hair-cells  on  that  particular  part  of  the  membrane  would 
be  stimulated,  and  the  note  might  be  appreciated  in  its 
true  position  in  the  scale. 

We  must  now  pass  on  to  consider  the  sense  of  hearing 
in  animals.  That  the  mammalia  have  this  sense  well 
developed  is  a  matter  of  familiar  observation,  and  in  some 
of  them,  such  as  the  horse  and  the  deer,  it  is  exceedingly 


264  Animal  Life  and  Intelligence. 

acute.  The  form  and  movements  of  the  external  ear  also 
enable  many  of  the  mammalia  to  collect  and  attend  to 
sounds  from  special  directions.  The  mammalia  possess 
also  the  power  of  tone-discrimination,  as  is  shown  by  the 
fact  that  our  domesticated  animals  recognize  different 
modulations  of  the  human  voice,  and  that  wild  creatures 
distinguish  tones  or  noises  of  different  quality.  A  New- 
foundland dog,  possessed  by  a  friend  of  mine,  always 
howled  when  the  tenor  D  was  struck  on  the  piano,  or  sung. 
And  Theophile  Gautier  reports  that  one  of  his  cats  could 
not  endure  the  note  G,  and  always  put  a  reproving  and 
silencing  paw  on  the  mouth  of  any  one  who  sang  it. 

In  birds  the  sense  of  hearing  is  not  only  very  sensitive, 
but  the  power  of  discrimination  is  exceedingly  delicate. 
No  one  who  has  watched  a  thrush  listening  for  worms  can 
doubt  that  her  ear  is  highly  sensitive.  The  astonishing 
accuracy  with  which  many  birds  imitate,  not  only  the  song 
of  other  birds,  but  such  unwonted  sounds  as  the  clink  of 
glasses  or  the  ring  of  quoits,  shows  that  the  delicacy  in 
discrimination  has  reached  a  high  level  of  development. 
In  birds,  however,  the  cochlear  canal  has  not  the  same 
development  that  it  has  in  mammals,  and  there  are  no 
arched  rods — no  organs  of  Corti. 

Nothing  special  is  to  be  noted  concerning  the  sense  of 
hearing  in  the  reptiles,  amphibia,  and  fishes.  In  all  (with 
the  exception  of  the  lowly  lancelet)  the  auditory  organ  is 
developed.  We  shall,  however,  presently  see  reason  to 
question  whether  the  possession  of  an  "  auditory  organ," 
with  well-developed  semicircular  canals,necessarilyindicates 
the  power  of  hearing.  And  Mr.  Bateson's  recent  experi- 
ments at  Plymouth*  seem  to  indicate  that  fishes  are  not  so 
sensitive  in  this  respect  as  anglers  f  are  wont  to  believe. 
"  The  sound  made  by  pebbles  rattling  inside  an  opaque 
glass  tube  does  not  attract  or  alarm  pollack ;  neither  are 
they  affected  by  the  sharp  sound  made  by  letting  a  hanging 

*  Journal  of  Marine  Biological  Association,  New  Series,  vol.  i.  No.  3,  p.  251. 
t  Of  course,  anglers  will  say  that  what  may  be  true  for  pollack  and  other 
coarse  and  vulgar  sea-fish  does  not  apply  to  King  Salmon  or  Prince  Trout. 


The  Senses  of  Animals.  265 

stone  tap  against  an  opaque  glass  plate  standing  vertically 
in  the  water."  Carp  at  Potsdam  are,  indeed,  said  to  come 
to  be  fed  at  the  sound  of  a  bell.  But  Mr.  Bateson  well 
remarks  that  this  "  can  scarcely  be  taken  to  prove  that  the 
sound  of  the  bell  was  heard  by  them,  unless  it  be  clearly 
proven  that  the  person  about  to  feed  them  was  hidden  from 
their  sight."  There  is  clearly  room  for  further  observation 
and  experiment  in  this  matter. 

Turning  to  the  invertebrata,  we  find,  even  in  creatures 
as  low  down  in  the  scale  of  life  as  jelly-fish,  around  the 
margin  of  the  umbrella  in  certain  medusae,  simple  auditory 
organs.  In  some  cases  they  are  pits  containing  otoliths 
(minute  calcareous  or  other  bodies,  which  are  supposed  to 
be  set  a-dance  by  the  sound-vibrations)  ;  in  others  there  is 
a  closed  sac  with  one  or  more  otoliths ;  in  others,  again, 
they  are  modified  tentacles,  partially  or  completely  enclosed 
in  a  hood.  All  these  are  generally  regarded  as  auditory, 
there  being  specially  modified  cells  of  the  nature  of  hair- 
cells.  We  shall  see,  however,  that  another  interpretation 
of  organs  containing  otoliths  is  at  any  rate  possible.  For 
the  present,  we  will  follow  the  usual  interpretation,  and 
regard  them  as  auditory. 

Vesicular  organs  containing  otoliths  are  found  near  the 
cerebral  ganglia  in  some  of  the  worms  and  their  relations. 
But  the  common  earthworm,  though  it  appears  to  be  sensi- 
tive to  sound,  does  not  appear  to  have  any  such  organs. 

Molluscan  shell-fish  are  generally  provided  with  auditory 
organs.  In  the  fresh-water  mussel  it  is  found  in  the 
muscular  foot.  It  can  be  more  readily  seen  in  the  Cyclas, 
if  the  transparent  foot  of  this  small  mollusc  be  examined 
under  the  microscope.  It  is  a  small  sac  containing  an 
otolith.  Mr.  Bateson  found  that  the  mollusc  Anomia  "can 
be  made  to  shut  its  shell  by  smearing  the  finger  on  the 
glass  of  the  tank  so  as  to  make  a  creaking  sound.  The 
animals  shut  themelves  thus  when  the  object  on  which  they 
were  fixed  was  hung  in  the  water  by  a  thread."  In  the 
snail  and  its  allies  the  auditory  sac  is  found  in  close 
connection  with  the  nerve-collar  that  surrounds  the  gullet. 


266  Animal  Life  and  Intelligence. 

In  the  cuttle-fishes  it  is  found  embedded  in  the  cartilage  of 
the  head. 

In  the  lobster  or  crayfish  the  auditory  organs  are  found 
at  the  base  of  the  smaller  feelers  or  antennules.  They  are 
little  sacs  formed  by  an  infolding  of  the  external  integument 
(see  Fig.  26,  p.  259).  Beautifully  feathered  auditory  hairs 
project  into  the  sac  along  specialized  ridges,  and  the  sac 
in  many  cases  contains  grains  of  sand  which  play  the  part 
of  otoliths.  Hensen  seems  to  have  proved  that  shrimps 
collect  the  grains  of  sand  and  place  them  in  the  auditory 
sac  for  this  purpose.  The 
curious  shrimp-like  Mysis  has 
two  beautiful  auditory  sacs  in 
its  tail.  These  are  provided 
with  auditory  hairs.  Hensen 


scope  while  a  musical  scale  was 
sounded,  and  found  that  the  special  hairs  responded  each 
to  a  certain  note.  When  this  particular  note  was  sounded 
the  hair  was  thrown  into  such  violent  vibration  as  to  become 
invisible,  but  by  other  notes  it  was  unaffected. 

Passing  now  to  insects,  we  may  first  note  that  grass- 
hoppers and  crickets  have  an  auditory  organ  on  the  front 
leg.     These  are  provided  with  tympanic  mem- 
branes, and  the  breathing-tubes,  or  tracheae, 
are  so  arranged  that  the  pressure  of  the  air 
is  equalized  on  the  two  sides  of  the  mem- 
brane—just as  in  us  and  other  vertebrates  the 
same   end  is  effected  by  a  tube  which  runs 
from  the  interior  of  the  drum  of  the  ear  to  the 
Fig.  29.—  Leg   mouth-cavity  (see  Fig.  27).  In  the  organ  within 

of  grasshopper.    ..,.,.  ,       ,,       ,  ,,  ,          j  , 

ty.,  tympanic  mem-  ™e  ^6§  there  ls  a  g*OUp  of  Cells,  followed  by  a 

brane.  row  Of  simiiar  Ceu8  which  diminish  regularly  in 
size  from  above  downwards.  Each  is  in  connection  with  a 
nerve-fibril,  and  contains  a  delicate  auditory  rod.  It  has 
been  suggested  that  the  diminution  in  size  of  the  cells  may 
have  reference  to  the  appreciation  of  different  notes,  but 
nothing  definite  is  known  on  the  matter.  Ants,  too,  have 


The  Senses  of  Animals.  267 

an  auditory  organ,  as  shown  by  Sir  John  Lubbock,  in  the 
tibia  of  the  front  leg.  But  in  locusts  it  is  situated  on  the 
first  segment  of  the  abdomen.  In  flies  there  are  a  number 
of  vesicles,  generally  regarded  as  auditory  (but  by  some  as 
olfactory),  at  the  base  of  the  rudimentary  hind  wings — the 
so-called  halteres,  or  balancers. 

Observation  seems  to  point  to  the  fact  that  in  most 
insects  the  sense  of  hearing  is  lodged  in  the  feelers,  or 
antennae.  Kirby  made  the  following  observation  on  a  little 
moth  :  "  I  made,"  he  says,  "  a  quiet,  not  loud,  but  distinct 
noise ;  the  antenna  nearest  to  me  immediately  moved 
towards  me.  I  repeated  the  noise  at  least  a  dozen  times, 
and  it  was  followed  every  time  by  the  same  motion  of  that 
organ,  till  at  length  the  insect,  being  alarmed,  became 
more  agitated  and  violent  in  its  motions."  Hicks  wrote, 
in  1859,  "  Whoever  has  observed  a  tranquilly  proceeding 
Capricorn  beetle  which  is  suddenly  surprised  by  a  loud 
sound,  will  have  seen  how  immovably  outward  it  spreads 
its  antennae,  and  holds  them  porrect,  as  it  were,  with  great 
attention,  as  long  as  it  listens."  The  same  observer 
described  certain  highly  specialized  organs  in  the  antennae 
of  the  hymenoptera  (ants,  bees,  and  wasps),  which  he  thus 
describes  :  "  They  consist,"  he  says,  "  of  a  small  pit  lead- 
ing into  a  delicate  tube,  which,  bending  towards  the  base, 
dilates  into  an  elongated  sac  having  its  end  inverted."  Of 
these  remarkable  organs,  Sir  John  Lubbock  says  there  are 
about  twelve  in  the  terminal  segment,  and  he  has  suggested 
that  they  may  serve  as  microscopic  stethoscopes. 

Mayer,  experimenting  with  the  feathered  antenna  of 
the  male  mosquito,  found  that  some  of  the  hairs  were 
thrown  into  vigorous  vibration  when  a  note  with  512 
vibrations  per  second  was  sounded.  And  Sir  John  Lubbock, 
who  quotes  this  observation,  adds,*  "It  is  interesting 
that  the  hum  of  the  female  gnat  corresponds  nearly  to  this 
note,  and  would  consequently  set  the  hairs  in  vibration." 
The  same  writer  continues,  "  Moreover,  those  auditory 
hairs  are  most  affected  which  are  at  right  angles  to  the 
*  "  Senses  of  Animals,"  p.  117, 


268  Animal  Life  and  Intelligence. 

direction  from  which  the  sound  comes.  Hence,  from  the 
position  of  the]  antennae  and  the  hairs,  a  sound  would  act 
most  intensely  if  it  is  directly  in  front  of  the  head. 
Suppose,  then,  a  male  gnat  hears  the  hum  of  a  female  at 
some  distance.  Perhaps  the  sound  affects  one  antenna 
more  than  the  other.  He  turns  his  head  until  the  two 
antennae  are  equally  affected,  and  is  thus  able  to  direct  his 
flight  straight  towards  the  female." 

It  is  difficult  to  determine  the  range  of  hearing  in  the 
lower  organisms.  But  it  is  quite  possible,  nay,  very 
probable,  that  the  superior  limit  of  auditory  sensation  is 
much  more  extended  in  insects  than  it  is  in  man.  We  know 
that  many  insects,  such  as  the  cicadas,  the  crickets  and 
grasshoppers,  many  beetles,  the  death's-head  moth,  the 
death-watch,  and  others,  make,  in  one  way  or  another, 
sounds  audible  to  us.  But  there  may  be  many  insect- 
sounds — we  may  not  call  them  voices — which,  though 
beyond  our  limits  of  hearing,  are  nevertheless  audible  to 
insects.  At  the  other  end  of  the  scale,  on  the  other  hand, 
slow  pulsations  may  be  appreciated — for  example,  by 
aquatic  creatures — by  means  of  what  we  term  the  auditory 
organs,  in  a  way  that  is  not  analogous  to  the  sensation  of 
sound  in  us.  It  may  be  noted  that  auditory  organs  are 
dotted  about  the  body  somewhat  promiscuously  in  the 
various  invertebrates.  We  have  seen  that  auditory  organs, 
or  what  are  generally  believed  to  be  such,  are  found  in  the 
foot  of  bivalves,  in  the  antennules  of  lobsters,  in  the  fore 
legs  of  crickets  and  ants,  in  the  abdomen  of  locusts,  in  the 
balancers  of  flies,  and  in  the  tail  of  Mysis.  But  when  we 
come  to  consider  the  matter,  there  is  no  reason  why  the 
organ  of  hearing  should  be  in  any  special  part  of  the  body. 
The  waves  of  sound  rain  in  upon  the  organism  from  all  sides. 
There  is  no  great  advantage  in  having  the  organs  of  hearing 
in  the  line  of  progression,  as  with  sight,  where  the  rays 
come  in  right  lines ;  nor  in  having  them  in  close  association 
with  the  mouth,  as  in  the  case  of  the  organ  of  smrfll. 

Closely  connected  with  the  organ  of  hearing  in  vertebrates 
is  the  organ  of  another  and  but  recently  recognized  sense. 


The  Senses  of  Animals.  269 

In  briefly  describing  the  auditory  apparatus  in  man,  mention 
was  made  of  three  curved  membranous  loops,  the  so-called 
semicircular  canals.  A  few  more  words  must  now  be  said 
about  them  and  the  membranous  sac  with  which  they  are 
connected. 

The  sac  lies  in  a  somewhat  irregular  cavity  in  a  bone 
at  the  side  of  the  head,  in  the  walls  of  which  are  five 
openings  leading  into  curved  tunnels  in  the  bone  in  which 
lie  the  membranous  loops.  The  planes  in  which  the  three 
semicircular  canals  lie  are  nearly  at  right  angles  to  each 
other,  and  they  are  called  respectively  the  horizontal, 
the  superior,  and  the  posterior.  The  two  latter  unite  at 
one  end  before  they  reach  the  sac  ;  hence  there  are  five,  and 
not  six,  openings  into  the  cavity.  At  one  end  of  each  semi- 
circular canal  is  a  swelling,  or  ampulla,  in  each  of  which  is 
a  ridge,  or  crest,  abundantly  supplied  with  hair-cells.  And 
in  a  little  recess  in  the  sac  there  is,  occupying  its  floor,  its 
front  wall,  and  part  of  its  outer  wall,  a  patch  of  hair-cells 
covered  by  a  gelatinous  material  with  numerous  small 
crystalline  otoliths.  The  only  other  point  that  calls  for 
notice  is  that  the  membranous  sac  does  not  fit  closely  in 
the  bony  cavity  in  which  it  lies,  while  the  diameter  of  the 
membranous  semicircular  canals  is  considerably  less  than 
that  of  their  bony  tunnels,  except  at  the  ampullae,  or  swellings, 
where  they  fit  pretty  closely.  Both  the  bony  cavity  and  the 
membranous  labyrinth  (as  it  is  called)  are  filled  with  fluid. 

From  its  close  connection  with  the  organ  of  hearing, 
this  apparatus  was  for  long  regarded  as  in  some  way 
auditory  in  its  function,  and  it  was  surmised  that  it  enabled 
us  to  perceive  the  direction  from  which  the  sound  came. 
But  how  it  could  do  so  was  not  clear.  In  1820  M. 
Flourens  made  the  observation  that  the  injury  or  division 
of  a  membranous  canal  gave  rise  in  the  patient  to  rotatory 
movements  of  the  animal  round  an  axis  at  right  angles  to 
the  plane  of  the  divided  canal ;  and  he,  therefore,  suggested 
that  the  canals  might  be  concerned  in  the  co-ordination  of 
movement.  They  are  now  regarded  as  the  organs  of  a 
sense  of  rotation  or  acceleration, 


270 


Animal  Life  and  Intelligence. 


That  we  have  such  a  sense  of  rotation  has  been  proved 
experimentally.*  Let  a  man,  blindfolded,  sit  on  a  smooth- 
running  turn-table.  When  it  begins  to  rotate  he  feels  that 
he  is  being  moved  round,  but  if  the  rotation  be  continued 
at  the  same  rate,  this  feeling  quickly  dies  away.  If  the 
rotation  be  increased,  he  again  feels  as  if  he  were  being 
moved  round,  but  this  again  soon  dies  away.  Further  in- 
crease gives  a  fresh  sensation,  which  in  turn  subsides,  and 
the  man  may  then  be  spinning  round  rapidly,  and  be  per- 
fectly unconscious  of  the  fact.  He  is  only  aware  that  he  has 
been  gently  turned  round  a  little  two  or  three  times.  Now 
let  the  speed  of  rotation  be  slackened.  He  has  a  sensation 
of  being  gently  turned  round  a  little  in  the  opposite  direction. 
Each  time  the  speed  is  lessened  he  has  this  sense  of  being 
turned  the  reverse  way.  From  these  experiments  we  see 
that  what  we  are  conscious  of  is  change  of  rate  of  rotation, 
or,  in  technical  language,  acceleration,  positive  or  negative. 

From  Professor  Crum  Brown's  paper  in  Nature  I  tran- 
scribe, with  some  verbal  modifications,  his  account  of  how 
the  semicircular  canals  enable  us  to  feel  these  changes  of 
SC. 


A     /'• 

Fig.  30. — Diagram  of  semicircular  canals. 

A.  bony  labyrinth  of  human  ear  (after  Sommering).    c,  c.,  the  cochlea;  *.c.,  superior 
semicircular  canal ;  p.c.,  posterior   semicircular  canal ;   h.c.,  horizontal  semicircular  canal ; 
a,  a,  a,  their  swellings,  or  ampullae;  f.o.,  f.r.,  fenestra  ovalis  and  rotunda  (oval  and  round 
windows)  in  the  vestibule. 

B.  Diagram  of  semicircular  canal  to  illustrate  effect  of  rotation.     The  large  arrows  indicate 
the  direction  of  the  rotation.     The  small  arrow  to  the  left  indicates  the  resulting  flow  of  the 
inner  fluid  into  the  ampulla ;  that  to  the  right,  the  flow  of  the  outer  fluid  into  the  vestibule. 

motion.  Let  us  consider  the  action  of  one  canal.  If  the 
head  be  rotated  about  a  line  at  right  angles  to  the  plane  of 
the  canal,  with  the  ampulla  leading,  there  will  be  a  tendency 

*  See  a  very  interesting  and  lucid  paper  by  Professor  Crum  Brown,  whose 
name  is  intimately  connected  with  this  subject,  in  Nature,  vol.  il.  p.  449. 


The  Senses  of  Animals.  271 

for  the  fluid  within  the  sac  to  flow  into  the  ampulla,  and 
for  the  fluid  around  the  semicircular  canal  to  flow  into  the 
cavity  in  which  the  sac  lies.  These  movements  will  con- 
spire to  stretch  the  membranous  ampulla,  and  thus  to 
stimulate  the  hair-cells.  This  stretching  will  not  take 
place  in  that  canal  if  the  rotation  be  in  the  reverse  direction. 
But  on  the  opposite  side  of  the  head  is  another  canal  in 
the  same  plane,  but  turned  the  other  way.  In  the  reversed 
rotation  the  ampulla  in  this  canal  will  lead,  and  its  hair- 
cells  will  be  stimulated.  Thus  by  means  of  the  two  canals 
on  either  side  of  the  head  in  the  same  plane,  rotation  in 
either  direction  can  be  appreciated.  And  since  there  are 
two  other  pairs  of  semicircular  canals  in  two  other  planes, 
rotation  in  any  direction  will  be  recognized  by  means  of 
one  or  more  of  the  six  canals. 

It  is  thus  by  means  of  the  semicircular  canals  that  we 
can  appreciate  acceleration  of  rotatory  motion.*  But  we 
can  also  appreciate  acceleration  of  movements  of  translation 
— forwards  or  backwards,  up  or  down.  And  Professor 
Mach  has  suggested  that  it  is  through  the  stimulation  of 
the  hair-cells  in  the  patch  in  the  sac  itself  (the  so-called 
macula  acustica)  that  we  are  able  to  appreciate  these  changes. 
The  otoliths,  held  loosely  and  lightly  in  position  by  the 
gelatinous  substance  in  which  they  are  embedded,  may, 
through  their  inertia,  aid  in  the  stimulation  of  the  sense- 
hairs. 

And  this  naturally  suggests  the  question  whether  those 
sense-organs  in  the  invertebrates  which  contain  otoliths 
may  not  be  regarded  with  more  probability  as  organs  for 
the  appreciation  of  changes  of  motion  than  as  auditory 
organs.  This  for  some  years  has  been  my  own  belief.  I 
have  always  felt  a  difficulty  in  understanding  how  the 
otoliths  are  set  a-dance  by  auditory  vibrations.  But  their 
inertia  would  materially  aid  in  the  appreciation  of  changes 
of  motion.  In  some  forms  the  otoliths  are  held  in  suspen- 
sion in  a  gelatinous  material.  In  others — the  molluscs, 

*  It  is  interesting  to  note  that  in  the  blind-fish  (Amblyopsis  spelxus)  the 
semicircular  canals  are,  according  to  Wyman,  unusually  large. 


2  72  Animal  Life  and  Intelligence. 

for  example — the  otolith  (which  is  generally  single)  is 
retained  in  a  free  position  by  ciliary  action.  In  aquatic 
creatures  an  organ  for  the  appreciation  of  changes  of 
motion  might  be  of  more  service  than  an  auditory  organ. 
And  if  one  be  permitted  to  speculate,  one  may  surmise  that 
the  sense  of  hearing  may  be  a  refinement  of  the  sense 
through  which  changes  of  motion  are  appreciated.  First 
would  come  a  sense  of  movements  of  the  organism  in  the 
medium  through  the  stimulation  of  the  sense-hairs  by 
the  relative  motion  of  the  otolith  ;  then  these  sense-hairs, 
with  increased  delicacy,  might  appreciate  shocks  in  the 
medium;  and,  eventually,  those  more  delicate  shocks 
which  we  know  as  auditory  waves.  In  this  way  we  might 
account  for  the  fact  that  in  the  vertebrates  the  same 
organ,  through  different  parts  of  its  structure,  appreciates 
both  change  of  motion  and  auditory  vibrations.  And  thus 
the  organs  in  the  invertebrata  which  are  generally  regarded 
as  auditory,  and  for  which  has  been  suggested  the  function 
of  reacting  to  changes  of  motion,  may,  in  truth,  subserve 
both  purposes — may  be  organs  in  which  the  differentiation 
I  have  hinted  at  is  taking  place. 

Sight,  like  hearing,  is  a  telsesthetic  sense.  Through  it 
we  become  aware  of  certain  vibratory  states  of  more  or  less 
distant  objects.  The  medium  by  means  of  which  these 
vibrations  are  transmitted  is  not,  as  in  the  case  of  hearing, 
the  air,  but  the  aether  which  pervades  all  space.  The  rate 
of  transmission  is  about  186,000  miles  in  a  second.  That 
which  answers  in  vision  to  pitch  in  hearing  is  colour.  The 
lowest,  or  gravest,  light-tone  to  which  we  are  sensitive  is 
deep  red,  where  the  number  of  vibrations  per  second  is 
about  370  billions  (370,000,000,000,000).  The  highest,  or 
most  acute,  light-tone  is  violet,  with  about  833  billion 
vibrations  in  a  second.  If  white  light  be  passed  through 
a  prism,  the  rays  are  classified  according  to  their  vibration- 
periods,  and  are  spread  out  in  a  spectrum,  or  band  of 
rainbow  colours.  But  different  individuals  vary,  as  we 
shall  presently  see,  in  their  sensibility  to  the  lowest  and 


The  Senses  of  Animals.  273 

the  highest  vibrations.  Some  people  are,  moreover, 
relatively  or  absolutely  insensible  to  certain  colours, 
generally  either  red  or  green.  Such  persons  are  said  to 
be  colour-blind.  When  the  rainbow  colours  are  combined 
in  due  proportion,  or  when  pairs  or  sets  of  them  are  com- 
bined in  certain  ways,  white  light  is  produced. 

We  saw  that  in  the  case  of  sound-waves,  when  the 
number  of  vibrations  in  a  second  is  doubled,  the  sound  is 
raised  in  pitch  by  an  octave.  Using  this  term  in  an 
analogous  way  for  colour-tones,  we  may  say  the  range  in 
average  vision  is  about  one  octave — that  is,  from  about 
400  billion  to  about  800  billion  vibrations  in  a  second. 
But,  though  these  are  the  limits  in  human  vision,  we  know 
of  the  existence  of  many  octaves  of  radiant  energy 
physically  in  continuity  with  the  light-vibrations.  Photo- 
graphy has  made  us  acquainted  with  ultra-violet  vibrations 
up  to  about  1600  billions  per  second — an  octave  above  the 
violet.  And  Professor  Langley's  observations  with  the 
bolometer  indicate  the  existence  of  waves  with  as  low  a 
vibration-period  as  one  billion  per  second,  and  even  here, 
in  all  probability,  the  limit  has  not  been  reached.  To  the 
vibrations  more  rapid  than  those  that  are  concerned  in 
the  sensation  of  violet,  the  human  organism  is  apparently 
in  no  manner  sensitive.  But  to  infra-red  vibrations  down 
to  about  thirty  billions  per  second  the  nerves  of  the  skin 
respond  through  the  temperature- sense.  We  shall  have  to 
return  to  these  limits  of  sensation  at  the  close  of  this 
chapter. 

The  human  eye  is  a  nearly  spherical  organ,  capable  of 
tolerably  free  movements  of  rotation  in  its  socket.  What 
we  may  call  the  outer  case,  which  is  white  and  opaque 
elsewhere,  is  quite  transparent  in  front.  Through  this 
transparent  window  may  be  seen  the  coloured  iris,  in  the 
centre  of  which  is  a  circular  aperture,  the  pupil.  The  size 
of  the  pupil  changes  with  the  amount  of  light — it  dilates 
or  contracts,  according  as  the  light  is  less  or  more  intense. 
Just  behind  it,  and  still  in  the  front  part  of  the  eye,  is  the 
transparent  lens,  the  convexity  of  the  anterior  surface  of 


274 


Animal  Life  and  Intelligence. 


which  can  be  altered  in  the  accommodation  of  the  organ 
for  near  or  far  vision.     The  space  between  the  lens  and 


Fig.  31.  —  The  human  eye. 
Horizontal  section,  to  show  general  structure. 

iris  and  the  corneal  window  of  the  eye  is  filled  with  a 
watery  fluid.  Behind  the  lens  there  is  a  transparent,  semi- 
fluid, jelly-like  material,  filling  the  rest  of 
,£  the  chamber  of  the  eye.  At  the  back  of  the 
eye  is  spread  out  the  sensitive  membrane 
—  the  retina.  The  structure  of  this  mem- 
brane is  very  complicated,  and  cannot  be 
described  here.  It  is,  however,  indicated 
in  Fig.  32.  For  our  present  purpose  it  is 
sufficient  to  note  that  here  are  the  end- 
organs  of  the  optic  nerve  ;  that  these  con- 
.  sist  of  a  number  of  delicate  rods  and  cones  ; 

Fig.  32.—  Retina  of         >.,... 

the  eye.  Enlarged  and  that  these  rods  and  cones  do  not  face 


in  the  direction  from  wbicn  the  Kght  comes, 
.,  back  of  retina  next  but  face  towards  the  back  of  the  eyeball, 

the    outer   coat;    Z.r.c.,        .  .  i     i         i     i  •      a         i  i 

layer  of  rods  and  cones;  where  a  pigmented  substance  is  developed. 

i.l.,  intermediate  layers  ;    „,  ,  -.    .  .  ,  ,     ,  , 

z.p.c.,  layer  of  ganglion-  The  rays  of  light  are  thus  focussed  through 

cells;    Z.n./.,    layer    of  .  *.*_•'•  L    a         i     L 


.  *.*_••  L    a         i     L 

.,  front  of  the  retina  on  to  this  pigmented  substance  ; 

retina,  the  surface  turned  , 

towards  the  pupii.         the  ends  of  the  rods  and  cones  are  stimu- 
lated ;  and  the  stimulation  is  handed  on,  augmented  in 


The  Senses  of  Animals.  275 

certain  intermediate  ganglia,  to  the  delicate  transparent 
nerve-fibres  in  the  front  of  the  retina.  These  collect  to  a 
certain  spot,  where  they  pass  through  the  retina  to  form  the 
optic  nerve.  Where  they  pass  through  the  retina  there  can, 
of  course,  be  no  rods  and  cones.  And  in  this  spot  there  is 
no  power  of  vision.  It  is  the  blind  spot.  The  reality  of  its 
existence  can  easily  be  proved.  Make  a  dot  on  a  piece  of 
writing-paper,  and  about  three  inches  to  the  left  of  it  place 
a  threepenny  or  sixpenny  bit.  Close  the  right  eye,  and  look 
with  the  left  eye  at  the  dot.  The  sixpenny  bit  will  also  be 
seen,  but  not  distinctly.  Keep  the  eye  fixed  on  the  dot, 
and  move  the  head  slowly  away  from  the  paper.  At  a 
distance  of  about  ten  inches  the  coin  will  completely  dis- 
appear from  view.  Its  image  then  falls  on  the  blind  spot. 

The  organ  of  vision,  then,  in  us  consists  of  an  essential 
sensory  membrane,  the  retina,  with  its  delicate  rods  and 
cones ;  and  an  accessory  apparatus  for  focussing  an  inverted 
image  on  to  the  sensitive  surface  of  the  retina.  The 
surface  is  not,  however,  equally  sensitive,  or,  in  any  case, 
does  not  give  an  equal  power  of  discrimination,  throughout 
its  whole  extent.  This  is  seen  in  the  experiment  above 
described.  When  we  look  at  the  dot  we  see  the  coin,  but 
not  distinctly.  The  area  of  clear  and  distinct  vision  is,  in 
fact,  very  small,  constituting  the  yellow  spot  about  ^  of 
an  inch  (2  millimetres)  long,  and  3^  of  an  inch  ('8  milli- 
metre) broad.  And  even  within  this  small  area  there  is  a 
still  more  restricted  area  of  most  acute  sensibility  only  T^Q 
of  an  inch  (-2  millimetre)  in  diameter.  Nevertheless, 
within  this  minute  area  there  are  some  two  thousand 
cones,  the  rods  being  here  absent.  In  carefully  examining 
an  object  we  allow  this  area  of  acute  vision  to  range  over 
it.  Hence  the  extreme  value  of  that  delicate  mobility 
which  the  eye  possesses— a  mobility  that  is  accompanied 
by  muscular  sensations  of  great  nicety. 

We  saw  that  the  sense  of  touch  in  the  tongue  is 
sufficiently  delicate  to  enable  us  to  recognize,  as  two, 
points  of  contact  separated  by  ^5  of  an  inch  (I'l  milli- 
metre). What,  in  similar  terms,  is  the  delicacy  of  sight  ? 


276  Animal  Life  and  Intelligence. 

At  what  distance  apart,  on  the  most  delicate  part  of  the 
retina,  can  two  points  of  stimulation  be  recognized  as  dis- 
tinct from  each  other  ?  If  the  points  of  stimulation  be  not 
less  than  #oW  of  an  inch  ('004  millimetre)  apart,  they 
can  be  distinguished  as  two.  Below  this  they  fuse  into 
one.  The  diameter  of  the  end  of  a  single  cone  in  the 
yellow  spot  is  also  about  ^Vo  of  an  inch  (-0045  millimetre). 

With  regard  to  the  mode  in  which  the  stimulation  of 
the  retinal  elements  is  effected,  we  have  no  complete  know- 
ledge. Certain  observations  of  Boll  and  Kiihne,  however, 
show  that  when  an  animal  is  killed  in  the  dark  the  retina 
has  a  peculiar  purple  colour  which  is  at  once  destroyed  if 
the  retina  be  exposed  to  light.  If  a  rabbit  be  killed  at  the 
moment  when  the  image,  say,  of  a  window,  is  formed  on 
the  retina,  and  the  membrane  at  once  plunged  in  a  solution 
of  alum,  the  image  may  be  fixed,  and  an  "  optogram  "  of 
the  window  may  be  seen  on  the  retina.  The  discharge  of 
the  colour  of  the  retinal  purple  may  be  regarded  as  the 
sign  of  a  chemical  change  effected  by  the  impact  of  the 
light-vibrations.  But  in  the  yellow  spot  there  seems  to  be 
no  visual  purple.  It  is,  indeed,  developed  only  in  the  rods, 
not  in  the  cones.  Here,  probably,  chemical  or  metabolic 
changes  occur  without  the  obvious  sign  of  the  bleaching  of 
retinal  purple.  In  the  dusk-loving  owl  the  retinal  purple 
is  well  developed,  but  in  the  bat  it  is  said  to  be  absent. 

We  saw  that  in  the  case  of  hearing  the  auditory  organ 
is  fitted  to  respond  to  air-borne  vibrations  varying  from 
about  thirty  to  thirty  thousand  per  second.  And  though 
the  details  of  the  process  are  at  present  not  well  under- 
stood, it  is  believed  that  certain  parts  of  the  recipient 
surface  are  fitted  to  respond  to  low  tones,  other  parts  to 
intermediate  tones,  and  yet  others  to  high  tones.  Thus 
the  reception  is  serial.  If  there  be  two  pianos  near  each 
other,  accurately  in  tune,  any  note  struck  on  one  will  set 
the  corresponding  note  vibrating  in  the  other.*  The 
auditory  organ  may  be  likened  to  this  second  piano. 
Special  parts  respond  to  special  tones. 

*  The  dampers  must,  of  course,  be  lifted  by  depressing  the  loud  pedal. 


The  Senses  of  Animals.  277 

Now,  in  the  case  of  vision,  the  conditions  are  different. 
The  reception  cannot  be  serial.  As  I  range  my  eye  over 
a  flower-bed,  I  bring  the  area  of  distinct  vision  on  to  a 
number  of  different  colours,  and  these  are  seen  to  be  dis- 
tinct, though  they  are  received  on  the  same  part  of  the 
retinal  surface.  It  might,  perhaps,  be  suggested  that 
special  cones  were  set  apart  for  each  shade  of  colour.  But 
there  are  only  some  two  thousand  cones  in  the  central  area 
of  most  acute  vision,  and  Lyons  silk-manufacturers  prepare 
pattern  cards  containing  as  many  shades  of  coloured  silks. 
So  that  there  would  be  only  one  cone  to  each  colour.  And 
Herschel  thought  that  the  workers  on  the  mosaics  of  the 
Vatican  could  distinguish  at  least  thirty  thousand  different 
shades  of  colour!  There  are  also  many  phenomena  of 
colour-blending  which  show  that  colour-reception  cannot 
in  any  sense  be  serial. 

How,  then,  are  we  to  account  for  our  wide  range  of 
colour-sensation?  Just  as  the  blending  by  the  artist  on 
his  palette  of  a  limited  number  of  pigments  gives  him  the 
wide  range  of  colour  seen  on  his  canvas,  so  the  blending  of 
a  few  colour-tones  may  give  us  the  many  shades  we  are 
able  to  distinguish.  The  smallest  number  of  fundamental 
colour-tones  which  will  fairly  well  account  for  the  pheno- 
mena of  colour-vision,  is  three.  And  these  three  are  red, 
green,  and  blue  or  violet.  These  are  the  three  so-called 
primary  colours.  All  others  are  produced  from  these 
elements  by  blending. 

To  explain  our  ability  to  appreciate  differences  of  colour, 
then,  it  ..is  supposed,  on  the  hypothesis  of  Young  and  Von 
Helmholtz,  that  three  kinds  of  nerve-fibres  exist  in  the 
retina,  the  stimulation  of  which  gives  respectively,  red, 
green,  and  violet  in  consciousness.  Professor  McKendrick, 
interpreting  Von  Helmholtz,  gives  *  the  following  scheme : — 

"  1.  Bed  excites  strongly  the  fibres  sensitive  to  red,  and 
feebly  the  other  two. 

"2.  Yellow  excites  moderately  the  fibres  sensitive  to 
red  and  green,  feebly  the  violet. 

*  "  Special  Physiology,"  p.  636. 


278  Animal  Life  and  Intelligence. 

"  3.  Green  excites  strongly  the  fibres  sensitive  to  green, 
feebly  the  other  two. 

"4.  Blue  excites  moderately  the  fibres  sensitive  to 
green  and  violet,  feebly  the  red. 

"  5.  Violet  excites  strongly  the  fibres  sensitive  to  violet, 
feebly  the  other  two. 

"  6.  When  the  excitation  is  nearly  equal  for  the  three 
kinds  of  fibres,  the  sensation  is  white/' 

This  theory  cannot  be  regarded  as  more  than  a  pro- 
visional hypothesis.  Still,  by  its  means  we  can  explain 
many  colour-phenomena.  It  is  well  known,  for  example, 
that  if  we  gaze  steadily  at  a  red  object,  and  then  look  aside 
at  a  grey  surface,  an  after-image  of  the  object  will  be  seen 
of  a  blue  colour.  According  to  the  theory,  the  red  fibres 
have  been  tired  and  cannot  so  readily  answer  to  stimulation. 
Over  this  part  of  the  retina,  therefore,  the  effect  of  grey 
light  is  to  stimulate  normally  the  fibres  sensitive  to  green 
and  violet,  but  only  slightly  those  sensitive  to  red,  owing 
to  their  tired  condition.  The  result  will  be,  as  we  see  from 
the  above  scheme  (4),  the  sensation  of  blue.  Colour-blind 
people,  on  this  view,  are  those  in  whom  one  set  of  the  fibres, 
generally  the  red  or  the  green,  are  lacking  or  ill  developed. 

We  may,  perhaps,  with  advantage  restate  this  theory  in 
terms  of  chemical  change,  or  metabolism.  On  this  view 
three  kinds  of  "explosives"  are  developed  in  the  retinal 
cones ;  for  it  is  seemingly  the  cones,  rather  than  the  rods, 
which  are  concerned  in  colour-vision.  All  three  explosive 
substances  are  unstable ;  but  one,  which  we  may  call  E., 
is  especially  unstable  for  the  longer  waves  of  the  spectrum  ; 
another,  G.,  for  the  waves  of  mid-period ;  a  third,  V.,  for 
those  of  smallest  wave-length. 

Suppose  that  E.  only  were  developed.  If,  then,  we  were 
to  look  at  a  band  of  light  spread  out  in  spectrum  wave- 
lengths, we  should  see  a  band'*  of  monochromatic  r.  light. 
Its  centre  would  be  bright,  and  here  would  be  the  maximum 
instability  of  E.  On  either  side  it  would  fade  away.  The 

*  A  band  and  not  a  line,  because  K.  is  unstable  to  the  impact  of  a  con- 
iderable  range  of  light-vibratious. 


The  Senses  of  Animals.  279 

lateral  edges  of  the  spectrum  would  be  the  limits  of  the 
instability  of  E.  If  G.  only  were  developed,  we  should  see 
only  a  band  of  monochromatic  g.  light.  Its  centre  would 
not  coincide  with  that  for  E.,  but  would  lie  in  a  region  of 
smaller  wave-length.  Here  would  be  the  maximum  in- 
stability for  G.  On  either  side  the  green  would  fade  away. 
Its  lateral  edges  would  mark  the  limits  of  the  instability 
of  G.  But  though  their  centres  would  not  coincide,  the 
E.  band  and  the  G.  band  would  to  a  large  extent  overlap. 
Similarly  with  the  band  for  V.  It,  too,  would  have  its 
centre  of  maximum  instability  and  its  lateral  edges  of 
lessening  instability.  Its  centre  would  lie  in  a  region  of 
yet  smaller  wave-length  than  that  for  G.  And  the  v.  band 
would  overlap  the  green  and  the  red. 

Normally,  all  three  bands  are  developed,  and  their 
blended  overlapping  gives  the  colours  of  the  rainbow.  For 
this  reason  the  monochromatic  bands  r.,  g.,  and  v.  are  un- 
known to  us  in  experience.  All  the  colour-tints  we  know 
are  blended  tints.  What  we  call  full-red  light  causes 
strong  disruptive  change  in  E.,  but  decomposes  slightly 
G.,  and  probably  also,  but  in  much  less  degree,  V. 

Whether  E.,  G.,  and  V.  are  all  three  present  in  each 
cone,  or  whether  they  are  each  developed  in  separate 
cones,  we  do  not  know  for  certain.  Nor  are  we  certain 
that  there  are  separate  nerve-fibres  for  the  transmission  of 
stimuli  due  to  E.,  G.,  and  V. 

When  we  look  steadily  at  a  red  object  we  cause  the 
disruption  of  E. ;  and  since  it  takes  some  time  for  the 
reformation  and  reconstitution  of  this  explosive  substance, 
on  turning  the  eye  to  a  grey  surface,  G.  and  V.  are  alone, 
or  in  preponderating  proportions,  caused  to  undergo  dis- 
ruption. Hence  the  phenomena  of  complementary  after- 
images. It  is  not  merely  a  matter  of  the  tiring  of  certain 
nerve-fibres,  but  a  using-up  of  the  explosive  material  in 
certain  of  the  cones. 

What  is  called  colour-blindness  is  probably  due  to  one 
of  several  abnormal  conditions.  It  is  possible  that  in  some 
cases  E.,  G.,  or  V.  may  be  entirely  absent.  More  fre- 


280  Animal  Life  and  Intelligence. 

quently  they  are  in  abnormal  proportions.  They  probably 
vary  in  their  sensitiveness,  and  not  improbably  in  the 
wave-period  to  which  they  show  the  maximum  response. 

To  test  the  variation,  if  any,  in  the  limits  of  instability 
for  K.  and  V.,  or  in  any  case  in  the  limits  of  colour-vision 
at  the  red  end  and  at  the  violet  end  of  the  spectrum,  in 
apparently  normal  individuals,  my  friend  and  colleague, 
Mr.  A.  P.  Chattock,  made,  at  my  suggestion,  a  number  of 
observations  on  some  of  the  students  of  the  University 
College,  Bristol,  to  whom  my  best  thanks  are  due  for  their 
kind  willingness  to  be  submitted  to  experiment.  The  instru- 
ment used  *  was  a  single-prism  spectro-goniometer. 

In  the  accompanying  diagram  (Fig.  33)  the  results  of 
some  of  these  observations  are  graphically  shown.  The 
middle  part  of  the  spectrum,  between  the  wave-lengths 
420  and  740  millionths  of  a  millimetre,  is  omitted,  only  the 
red  end  and  the  violet  end  being  shown.  The  observations 
on  thirty-four  individuals,  seventeen  men  and  seventeen 
women,  all  under  thirty  years  of  age,  are  given  for  both 
eyes.  The  left-hand  vertical  line  of  each  pair  stands  for 
the  right  eye  in  each  case.  To  the  left  of  the  table  are 
placed  the  wave-lengths  in  millionths  of  a  millimetre. 

Take,  for  example,  the  first  pair  of  vertical  lines.     The 

*  Mr.  Chattock  has  kindly  supplied  me  with  the  following  note:— 

"  Headings  at  the  violet  end  were  taken  at  the  extremity  of  the  lavender 
rays,  at  the  point  where  the  faint  band  of  lavender  light  seemed  to  end  off 
about  half-way  across  the  field  of  view  (the  cross-wires  being  invisible). 

"  At  the  red  end  the  cross-wires  were  always  visible,  and  were  in  each 
case  set  to  the  point  where  the  top  horizontal  edge  of  the  spectrum  lost  its 
definition. 

"  Other  things  equal,  the  '  red '  readings  should  be  more  reliable  than  the 
violet,  therefore,  from  the  greater  definiteness  of  the  point  observed,  and  the 
means  of  observing  it.  But  against  this  has  to  be  set  off  the  fact  that  the 
extreme  violet  rays  were  spread  out  by  the  prism  used  more  than  eight  times 
as  much  as  the  red  rays. 

"  In  any  case,  the  wide  differences  observed  in  the '  red '  readings  are  much 
greater  than  could  have  been  due  to  misunderstanding  or  careless  observation 
— as  shown  by  setting  the  instrument  to  maximum  and  minimum  reading*, 
and  noting  the  very  obvious  difference  between  them  apparent  to  a  normal 
eye.  The  same  conclusion  is  rather  borne  out  by  the  closer  (average)  agree- 
ment between  the  two  eyes  of  the  same  individual  than  between  those  of 
different  persons. 

"  The  source  of  light  was  the  central  portion  of  an  ordinary  Argand  burner." 


The  Senses  of  Animals. 


281 


VIOLET 


282 


Animal  Life  and  Intelligence. 


individual  whose  colour-range  they  represent  could  detect 
red  light  in  the  spectrum  up  to  800  millionths  of  a  milli- 
metre wave-length  for  the  right  eye,  and  up  to  811  for  the 
left ;  and  could  detect  violet  light  down  to  403  and  404. 
Beyond  these  limits  all  was  dark.  But  the  last  individual 
in  the  series,  while  his  range  in  the  violet  was  about  the  same, 
could  only  detect  red  light  up  to  743  and  750  millionths  of 
a  millimetre.  His  spectrum  was  so  much  shorter. 

It  is  seen  that  there  is  more  variation  at  the  red  end 
than  at  the  violet  end  of  the  spectrum,  and  this  notwith- 
standing that  the  violet  rays  are  more  spread  out  by  the 
prism  than  the  red  rays.  It  is  seen  that  the  two  eyes  are 
often  markedly  different.  This  is  not  due  to  inaccuracy  of 
observation,  for  certain  individuals  in  which  this  occurred 
were  tested  several  times  with  similar  results.  It  is  seen 
that  the  variations  at  the  red  end  and  the  violet  end  are 
often  independent,  and  that  the  absolute  length  of  the 
visible  spectrum  differs  in  different  individuals. 

The  following  table  presents  these  observations  and  a 
few  others  in  another  light : — 

TABLE  OP  MAXIMA  AND  MINIMA  IN  WAVE-LENGTHS,  EXPRESSED  IN 
MILLIONTHS  OF  A  MILLIMETRE. 


VIOLET. 

RED. 

No.  of 

Highest. 

Mean. 

Lowest. 

Highest. 

Mean. 

Lowest. 

viduals. 

Women  under  30.. 

410-0 

402-75 

394-0 

811 

772-85 

743 

17 

Men          „ 

413-0 

405-0 

399-0 

811 

772-8 

743 

17 

Women  over  30  .  . 

4105 

406-65 

401-5 

792 

767-8 

743 

7 

Men          „     „    .. 

407-0 

404-5 

402-5 

787 

773-7 

758 

3 

J  right  eye 

406 

687 

N{  left  eye 

407 

717 

The  individual  N  showed  signs  of  colour-blindness, 
and  is  therefore  not  included  in  the  table,  but  entered 
separately.  He  was  unable  to  recognize  the  C  line  of  the 
hydrogen  spectrum  (wave-length  656),  which  was  brilliantly 
obvious  to  the  normal  eye. 


The  Senses  of  Animals.  283 

These  observations*  need  further  confirmation  and 
extension.  We  intend  to  continue  the  investigation  each 
session.  They  are,  however,  sufficient  to  show  that  in 
some  individuals  E.  undergoes  disruptive  change  on  the 
impact  of  light- waves  which  have  no  noticeable  effect  on 
the  retina  of  other  individuals. 

It  is  impossible  here  to  do  more  than  just  touch  the 
fringe  of  the  difficult  subject  of  colour-vision.  And  the 
only  further  fact  that  can  here  be  noticed  is  that  trichro- 
matic colour-vision  is  apparently  in  us  limited  to  the 
yellow-spot  and  its  immediate  neighbourhood.  Around 
this  is  an  area  which  is  said  to  be  bichromatic — all  of  us 
being,  for  this  area,  more  or  less  green-blind.  In  the 
peripheral  area  around  this,  colour  is  indistinguishable, 
and  we  are  only  sensitive  to  light  and  shade.  So  far  as 
the  structure  of  the  retina  is  concerned,  we  may  notice  in 
this  connection  that  in  the  central  region  of  most  complete 
trichromatic  vision  there  are  cones  only ;  around  the 
yellow  spot  each  cone  is  surrounded  by  a  circle  of  rods  ; 
and  further  out  into  the  peripheral  region  by  two,  three,  or 
more  circles  of  rods. 

Concerning  the  sense  of  sight  in  the  lower  mammals 
little  need  be  said.  In  many  cases  the  acuteness  of  vision 
is  remarkable.  Mr.  Eomanes's  experiments  on  Sally,  the 
bald-headed  chimpanzee  at  Eegent's  Park,  led  him  to 
conclude  that  she  was  colour-blind,  but  I  question  whether 
the  experiments  described  quite  justify  this  conclusion. 
Sir  John  Lubbock  was  unable  to  teach  his  intelligent  dog 
Van  to  distinguish  between  coloured  cards  ;  but  the  failure 
was  as  complete  when  the  cards  were  marked  respectively 
with  one,  two,  or  three  dark  bands.  We  are  not  justified, 
therefore,  in  ascribing  the  failure  to  colour-blindness.  The 
real  failure,  probably,  was  in  each  case  to  make  the  animal 
understand  what  was  wanted.  Bulls  are,  at  any  rate, 

*  The  variations  above  indicated  throw  light  on  a  fact  to  which  Lord  Ray- 
leigh  has  directed  attention.  The  yellow  of  the  spectrum  may  be  matched  by  a 
blending  of  spectral  red  and  spectral  green ;  but  the  proportions  in  which  these 
spectral  colours  must  be  mixed  differ  for  different  individuals.  The  comple- 
mentary colours  for  different  individuals  are  also  not  precisely  the  same. 


284  Animal  Life  and  Intelligence. 

credited  with  strong  colour-antipathies,  and  insect-eating 
mammals  are  probably  not  defective  in  the  colour-sense. 

It  is  said  that  nocturnal  animals,  such  as  mice,  bats, 
and  hedgehogs,  have  no  retinal  cones ;  and  if  the  cones 
are  associated  with  colour-vision,  they  may  not  improbably 
be  unable  to  distinguish  colours.  Some  moles  are  blind 
(e.g.  the  Cape  golden  mole).  But  the  common  European 
mole,  though  the  eyes  are  exceedingly  minute  (^  of  an 
inch  in  diameter),  has  the  organ  fairly  developed,  and  is 
even  said  not  to  be  very  short-sighted.  It  is  protected  by 
long  hairs  when  the  animal  is  burrowing,  and  is  only  used 
when  it  comes  to  the  surface  of  the  ground. 

It  is  probably  in  birds  that  vision  reaches  its  maximum 
of  acuteness.  A  tame  jackdaw  will  show  signs  of  uneasi- 
ness when  seemingly  nothing  is  visible  in  the  sky.  Pre- 
sently, far  up,  a  mere  speck  in  the  blue,  a  hawk  will  come 
within  the  range  of  far-sighted  human  vision.  Steadily 
watch  the  speck  as  the  hawk  soars  past,  until  it  ceases  to  be 
visible  ;  the  jackdaw  will  still  keep  casting  his  eye  anxiously 
upward  for  some  little  time.  He  may  be  only  watching 
for  the  possible  reappearance  of  the  hawk.  But  just  as 
he  saw  it  before  man  could  see  it,  so.  probably  he  still 
watches  it  after,  to  man's  sight,  it  has  become  invisible. 
So,  too,  for  nearer  minute  objects,  the  swift,  as  it  wheels 
through  the  summer  air,  presumably  sees  the  minute 
insects  which  constitute  its  food.  And  every  one  must 
have  noticed  how  domestic  fowls  will  pick  out  from  among 
the  sand-grains  almost  infinitesimal  crumbs. 

It  is  probable  that  the  area  of  acute  vision  is  much 
more  widely  diffused  over  the  retina  of  birds  than  it  is  with 
us.  In  any  case,  the  cones. are  more  uniformly  and  more 
abundantly  distributed  over  the  general  retinal  surface. 

An  exceedingly  interesting  and  important  peculiarity 
in  the  retina  of  birds,"  which  they  share  with  some  reptiles 
and  fishes,  is  the  development,  in  the  cones,  of  coloured 
globules.  "  The  retinae  of  many  birds,  especially  of  the 
finch,  the  pigeon,  and  the  domestic  fowl,  have  been  care- 
fully examined  by  Dr.  Waelchli,  who  finds  that  near  the 


The  Senses  of  Animals.  285 

centre  green  is  the  predominant  colour  of  the  cones,  while 
among  the  green  cones  red  and  orange  ones  are  somewhat 
sparingly  interspersed,  and  are  nearly  always  arranged 
alternately — a  red  cone  between  two  orange  ones,  and  vice 
versa.  In  a  surrounding  portion,  called  by  Dr.  Waelchli 
the  red  zone,  the  red  and  orange  cones  are  arranged  in 
chains,  and  are  larger  and  more  numerous  than  near  the 
yellow  spot ;  the  green  ones  are  of  smaller  size,  and  fill  up 
the  interspaces.  Near  the  periphery  the  cones  are  scattered, 
the  three  colours  about  equally  numerous  and  of  equal 
size,  while  a  few  colourless  cones  are  also  seen.  Dr. 
Waelchli  examined  the  optical  properties  of  the  coloured 
cones  by  means  of  the  micro-spectroscope,  and  found,  as 
the  colours  would  lead  us  to  suppose,  that  they  transmitted 
only  the  corresponding  portions  of  the  spectrum ;  and  it 
would  almost  seem,  excepting  for  the  few  colourless  cones 
at  the  peripheral  part  of  the  retina,  that  the  birds  examined 
must  have  been  unable  to  see  blue,  the  whole  of  which 
would  be  absorbed  by  their  colour-globules."  * 

These  facts  are  of  exceeding  interest.  They  seem  to 
show  that  for  these  birds  the  retinal  explosives  are  not  the 
same  as  for  us.  They  are  E.,  0.,  and  G.  Moreover,  the 
colour-globules  will  have  the  effect  of  excluding  the  pheno- 
mena of  overlapping.  For  each  kind  of  cone  the  spectrum 
must  be  limited  to  the  narrow  spectral  band  transmissible 
through  the  associated  colour-globule.  If  these  facts  be 
so,  it  is  not  too  much  to  say  that  the  colour- vision  of  birds 
must  be  so  utterly  different  from  that  of  human  beings, 
that,  being  human  beings,  we  are  and  must  remain 
unable  to  conceive  its  nature.  The  factors  being  different, 
and  the  blending  of  the  factors  by  overlap  being,  by 
specially  developed  structures,  lessened  or  excluded,  the 
whole  set  of  resulting  phenomena  must  be  different  from 
ours.  And  this  is  a  fact  of  the  utmost  importance  when 
we  consider  the  phenomena  of  sexual  selection  among 
birds,  and  those  theories  of  coloration  in  insects  which 
involve  a  colour-sense  in  birds. 

*  "  Col  our- Vision  and  Colour-Blindness,"  E.  Brudenell  Carter  (Nature, 
vol.  xlii.  p.  56). 


286  Animal  Life  and  Intelligence. 

Concerning  the  sense  of  sight  in  reptiles  and  in 
amphibians,  little  need  here  be  said.  At  near  distances 
some  of  them  undoubtedly  have  great  accuracy  of  vision. 
This  is,  perhaps,  best  seen  in  the  chamseleon.  In  this 
curious  animal  the  eyes  are  conical,  and  each  moves  freely, 
independently  of  the  other.  The  eyelids  encase  the  organ, 
except  for  a  minute  opening,  looking  like  a  small  ink-spot 
at  the  blunted  apex  of  the  cone.  The  animal  catches  the 
insects  on  which  it  feeds  by  darting  on  to  them  its  long 
elastic  tongue  and  slinging  them  back  into  the  mouth, 
glued  to  its  sticky  tip.  Its  aim  is  unerring,  but  it  never 
strikes  until  both  eyes  come  to  rest  on  the  prey,  and  great 
accuracy  of  vision  must  accompany  the  great  accuracy  of 
aim.  Frogs  and  toads  capture  their  prey  in  a  somewhat 
similar  way ;  and  a  great  number  of  reptiles  and  amphibians 
are  absolutely  dependent  for  their  subsistence  on  the  acute- 
ness  and  accuracy  of  their  vision,  which  is,  however,  on 
the  whole,  markedly  inferior  to  that  of  birds. 

In  fishes,  from  their  aquatic  habit,  the  lens  and  dioptric 
apparatus  are  specially  modified,  in  accordance  with  the 
denser  medium  in  which  they  live ;  and  one  curious  fish, 
the  Surinam  sprat,  is  stated  to  have  the  upper  part  of 
the  lens  suited  for  aerial,  and  the  lower  part  for  aquatic 
vision. 

Mr.  Bateson  *  has  made  some  interesting  observations 
on  the  sense  of  sight  in  fishes.  He  finds  that  in  the  great 
majority  of  fishes  the  shape  and  size  of  the  pupil  do  not 
alter  materially  in  accordance  with  the  intensity  of  the 
light.  The  chief  exceptions  are  among  the  Elasmobranchs 
(dog-fishes  and  skates).  In  the  torpedo  the  lower  limb  of 
the  iris  rises  so  as  almost  to  close  the  pupil,  leaving  a 
horizontal  slit  at  the  upper  part  of  the  eye.  In  the  rough 
dog-fish,  the  angel-fish,  and  the  nurse-hound,  the  pupil 
closes  by  day,  forming  merely  an  oblique  slit.  In  the 
skate  a  fern-like  process  descends  from  the  upper  limb  of 

*  Journal  of  Marine  Biological  Association,  New  Series,  vol.  i.  Xos.  2  and 
3.  His  experiments  with  regard  to  the  colour-sense  in  fishes  gave,  for  the 
most  part,  negative  results. 


The  Senses  of  Animals.  287 

the  iris.  The  contraction  in  these  cases  does  not  seem  to 
take  place  rapidly  as  in  land  vertebrates,  but  slowly  and 
gradually. 

Among  diurnal  fishes  belonging  to  the  group  of  the 
bony  fishes  (Teleosteans),  the  turbot,  the  brill,  and  the 
weever  have  a  semicircular  flap  from  the  upper  edge  of 
the  iris,  which  partially  covers  the  pupil  by  day,  but  is 
almost  wholly  retracted  at  night. 

None  of  the  fishes  observed  by  Mr.  Bateson  appears  to 
distinguish  food  (worms)  at  a  greater  horizontal  distance 
than  about  four  feet,  and  for  most  of  them  the  vertical 
limit  seemed  to  be  about  three  feet ;  but  the  plaice  at  the 
bottom  of  the  tank  perceived  worms  when  at  the  surface  of 
the  water,  being  about  five  feet  above  them.  Most  of  them 
exhibited  little  power  of  seeing  an  object  below  them.  But 
though  the  distance  of  clear  vision  seems  to  be  so  short  for 
small  objects  in  the  water,  many  of  these  fish  (plaice, 
mullet,  bream)  notice  a  man  on  the  other  side  of  the  room, 
distant  about  fifteen  feet  from  the  window  of  the  tank. 
The  sight  of  some  fishes,  such  as  the  wrasses  (Labridee),  is 
admirably  adapted  for  vision  at  very  close  quarters.  "I 
have  often  seen,"  says  Mr.  Bateson,  "a  large  wrasse  search 
the  sand  for  shrimps,  turning  sideways,  and  looking  with 
either  eye  independently,  like  a  chamaeleon.  Its  vision  is 
so  good  that  it  can  see  a  shrimp  with  certainty  when  the 
whole  body  is  buried  in  grey  sand  excepting  the  antennae 
and  antenna-plates.  It  should  be  borne  in  mind  that,  if 
the  sand  be  fine,  a  shrimp  will  bury  itself  absolutely, 
digging  with  its  swimmerets,  kicking  the  sand  forwards 
with  its  chelae,  finally  raking  the  sand  over  its  back,  and 
gently  levelling  it  with  its  antennae ;  but  if  the  least  bit 
be  exposed,  the  wrasses  will  find  it  in  spite  of  its  protective 
coloration." 

Although  it  is  probably  not  functional  in  any  existing 
form,  mention  must  here  be  made  of  the  median  or  pineal 
eye.  On  the  head  of  the  common  slow-worm,  or  blind- 
worm,  there  is  a  dark  patch  surrounding  a  brighter  spot. 


288 


Animal  Life  and  Intelligence. 


Fig.  34.— Pineal  eye. 


Varanus 
Spencer.) 


This  is  the  remnant  of  a  median  eye.  It  has  been  found  in 
varying  states  of  degeneration  in  many  reptiles  (Fig.  34),  and 
in  a  yet  more  vestigial  form  in  some  fishes  and  amphibia.  It 
is  connected  with  a  curious  struc- 
ture, associated  with  the  brain  of 
all  vertebrates,  and  called  the 
pineal  gland.  Descartes  thought 
that  this  was  the  seat  of  the  soul  ; 
but  modern  investigation  shows 
it  to  be  a  structure  which  has 
resulted  from  the  degeneration  of 
that  part  of  the  brain  which  was 
connected  with  the  median  eye. 
There  is  some  reason  to  suppose 

that>  in  ancient  life-forms>  like 

the  Ichthyosaurus,  and  Plesio- 
saurus,  and  the  Labyrinthodont  amphibians,  it  was  large 
and  functional.  In  any  case,  there  is  a  large  hole  in  the 
skull  (Fig.  35)  through  which  the  nervous  connection  with  the 
brain  may  have  been  established  .  The  structure  of  the  eye 

is  not  similar  to  that  of  the 
lateral  eye,  but  more  like  that 
of  some  of  the  invertebrates. 
To  these  invertebrates  we 
must  now  turn. 

Insects  have  eyes  of  two 
kinds.  If  we  examine  with  a 
lens  the  head  of  a  bee,  we 
shall  see,  on  either  side,  the 
large  compound  or  facetted 
eye  ;  but  in  addition  to  these 
there  is  on  the  forehead  or 
vertex  a  triangle  of  three 
small,  bright,  simple  eyes,  or 

npplli          TVlPQP    npplli     <TT    PVP- 
OCe111'        -^686    OC6111,  Or    BJQ 

J^     differ>    jn     different     in- 

sects,  as  to  the  details  of  their  structure  ;  but  in  general 


Fig.  35.—  Skull  of  Meianerpeton. 


A  Labyrinthodont  amphibian  from  the  Per- 
mian  of  Bohemia  (after  Fritsch).  X*.  Pa., 
the  parietal  foramen. 


The  Senses  of  Animals.  289 

they  consist  of  a  lens  produced  by  the  thickening  of  the 
integumentary  layer  which  is  at  the  same  time  rendered 

transparent.  Behind 
this  lies  the  so-called 
vitreous  body,  com- 
posed of  transparent 
A.  B.  y^V  cells,  and  then  follows 

Fig.  36.— Eyes  and  eyelets  of  bee.  the    retina,   in    which 

A.  Drone.    B.  Worker.  t^ere  are   a  number  of 

rods,  the  recipient  ends  of  which  are  turned  towards  the 
rays  of  light,  and  not  away  from  them  as  in  the  vertebrate, 
Spiders  have  from  six  to  eight  ocelli,  arranged  in  a  pattern 
on  the  top  of  the  head.  Facetted  eyes  are  not  found  in 
them. 

These  facetted  eyes,  which  are  found  in  both  insects 
and  Crustacea,  have  apparently  a  more  complex  structure 
than  the  ocelli.  Externally — in  the  bee,  for  example — the 
surface  is  seen  to  be  divided  up  into  a  great  number  of 
hexagonal  areas,  each  of  which  is  called  a  facet,  and  forms 
(in  some  insects,  but  not  in  all)  a  little  lens.  Of  these  the 
queen  bee  has  on  each  side  nearly  five  thousand ;  the  worker 
some  six  thousand ;  and  the  drone  upwards  of  twelve 
thousand;  while  a  dragon-fly  (JSschna)  is  stated  to  have 
twenty  thousand.  Beneath  each  facet  (in  transverse  section, 
Fig.  37)  is  a  crystalline  cone,  its  base  applied  to  the  lens,  its 
apex  embraced  by  a  group  of  elongated  cells,  in  the  midst 
of  which  is  a  nerve-rod  which  is  stated  to  be  in  direct  con- 
nection with  the  fibres  of  the  optic  nerve.  Dark  pigment  is 
developed  around  the  crystalline  cones.  And  retinal  purple 
is  said  to  be  present  in  the  cells  which  underlie  it. 

With  regard  to  these  facetted  eyes  there  has  been  much 
discussion.  The  question  is — Is  each  facetted  organ  an 
eye,  or  is  it  an  aggregate  of  eyes  ?  To  this  question  the 
older  naturalists  answered  confidently — An  aggregate.  A 
simple  experiment  seems  to  warrant  this  conclusion.  If 
the  facetted  surface  be  cleared  of  its  internal  structures 
(the  crystalline  cones,  etc.)  and  placed  under  the  microscope, 
each  lens  may,  at  a  suitable  distance  of  the  object-glass, 

u 


290  Animal  Life  and  Intelligence. 

be  made  to  give  a  separate  image  of  such  an  object  as  a 
candle  reflected  in  tbe  mirror  of  the  microscope.  If  each 
lens  thus  gives  an  image,  is  not  each  the  focussing  apparatus 

of  a  single  eye  ?  But  a 
somewhat  more  difficult 
experiment  points  in 
another  direction.  If  the 
facetted  cornea  be  re- 
moved with  the  crystalline 
cones  still  attached  (Gren- 
acher  was  able  to  do  it 
with  a  moth's  eye),  and 
placed  under  the  micro- 
scope, when  the  instru- 
ment is  focussed  at  the 
point  of  the  cone  (where 
Fig.  37.— Eye  of  fly.  the  nerve-rod  comes),  a 

Transverw  section  through  head.    (After  Hickson.)  gp()t    of  }ightj  and  Q()t  ftn 

image,  is  seen.  No  image  can  be  seen  unless  the  micro- 
scope be  focussed  for  the  centre  of  the  cone ;  and  here  there 
are  no  structures  capable  of  receiving  it  and  transmitting 
corresponding  waves  of  change  to  the  "  brain." 

But  what,  it  may  be  asked,  can  be  the  purpose  of  an 
eye-structure  which  gives,  not  an  image,  but  merely  a  spot 
of  light  ?  The  answer  to  this  question  can  only  be  found 
when  it  is  remembered  that  there  are  thousands  of  these 
facets  and  cones  giving  thousands  of  spots  of  light.  The 
somewhat  divergent  cones  and  facets  of  the  insect's  eye 
(Fig.  37)  embrace,  as  a  whole,  an  extended  field  of  vision ; 
each  has  its  special  point  in  that  field;  and  each  conveys 
to  the  nerve-rod  which  lies  beneath  it  a  stimulation  in 
accordance  with  the  brightness,  or  intensity,  or  quality  of 
that  special  point  of  the  field  to  which  it  is  directed.  The 
external  field  of  vision  is  thus  reproduced  in  miniature 
mosaic  at  the  points  of  the  crystalline  cones — thus  there  is 
produced  by  the  juxtaposition  of  contiguous  points  a  stippled 
image.  And  it  must  be  remembered  that,  even  in  human 
vision,  the  stimulation  is  not  that  of  a  continuum,  but  is 


The  Senses  of  Animals. 


291 


stippled  with  the  fine  stippling  of  the  ends  of  the  rods  and 
cones.  In  insect-vision  the  stippling  is  far  coarser,  and  the 
image  is  produced  on  different  principles. 

In  the  vertebrate  the  image  is  produced  by  a  lens ;  in 
the  insect's  eye,  by  the  elongated  cones.  How  this  is  effected 
will  be  readily  seen  with  the  aid  of  the  diagram.  At  a  b 
are  a  number  of  trans- 
parent rods,  separated  by 
pigmented  material  absorb- 
ent of  light.  They  repre- 
sent the  crystalline  cones. 
At  c  d  is  an  arrow  placed 
in  front  of  them  ;  at  e  f  is 


Fig.  38. — Diagram  of  mosaic  vision. 


a  screen  placed  behind 
them.  Eays  of  light  start 
in  all  directions  from  any  point,  c,  of  the  arrow ;  but  of  these 
only  that  which  passes  straight  down  one  of  the  trans- 
parent rods  reaches  the  screen.  Those  which  pass  obliquely 
into  other  rods  are  absorbed  by  the  pigmented  material. 
Similarly  with  rays  starting  from  any  other  point  of  the 
arrow.  Only  those  which,  in  each  case,  pass  straight  down 
one  of  the  rods  reach  the  screen.  Thus  there  is  produced  a 
reduced  stippled  image,  c'  d',  of  the  arrow. 

There  has  been  a  good  deal  of  discussion  as  to  the 
relative  functions  of  the  ocelli  and  the  facetted  eyes  of 
insects.  The  view  generally  held  is  that  the  ocelli  are 
specially  useful  in  dark  places  and  for  near  vision ;  while 
the  facetted  eyes  are  for  more  distant  sight  and  for  the 
ascertainment  of  space-relations.  How  the  two  sets  of 
impressions  are  correlated  and  co-ordinated  in  insect-con- 
sciousness, who  can  say  ?  * 

The  interesting  observations  of  Sir  John  Lubbock  seem 
to  show  that  insects  can  distinguish  between  different 
colours.  "  Amongst  other  experiments,"  he  says,f  "  I 

*  We  must  remember  how  largely  the  antennae  are  used  when  an  insect  is 
finding  its  way  about.  Watch,  for  example,  a  wasp  as  it  climbs  over  your 
plate.  If  the  antennae  be  removed,  it  seems  to  stumble  about  blindly.  The 
antennae  seem  almost  to  take  the  place  of  eyes  at  close  quarters. 

t  "  Senses  of  Animals,"  p.  194. 


29 2  Animal  Life  and  Intelligence. 

brought  a  bee  to  some  honey  which  I  placed  on  a  slip  of 
glass  laid  on  blue  paper,  and  about  three  feet  off  I  placed 
a  similar  drop  of  honey  on  orange  paper.  With  a  drop  of 
honey  before  her  a  bee  takes  two  or  three  minutes  to  fill 
herself,  then  flies  away,  stores  up  the  honey,  and  returns 
for  more.  My  hives  were  about  two  hundred  yards  from 
the  window,  and  the  bees  were  absent  about  three  minutes 
or  even  less.  After  the  bee  had  returned  twice,  I  transposed 
the  papers ;  but  she  returned  to  the  honey  on  the  blue 
paper.  I  allowed  her  to  continue  this  for  some  time,  and 
then  again  transposed  the  papers.  She  returned  to  the 
old  spot,  and  was  just  going  to  alight,  when  she  observed 
the  change  of  colour,  pulled  herself  up,  and  without  a 
moment's  hesitation  darted  off  to  the  blue.  No  one  who 
saw  her  at  that  moment  could  have  the  slightest  doubt 
about  her  perceiving  the  difference  between  the  two 
colours." 

Passing  now  to  the  Crustacea,  we  find  in  them  eyes  of 
the  same  type  as  in  insects ;  but  in  the  higher  Crustacea 
ocelli  are  absent.  In  the  crabs  and  lobsters  the  eyes  are 
seated  on  little  movable  pedestals;  in  the  former  the 
crystalline  cones  are  very  long,  in  the  latter  they  are  short. 
There  can  be  little  doubt  that  vision  is  by  no  means  want- 
ing in  acuteness  in  an  animal  which,  like  the  lobster,  can 
dart  into  a  small  hole  in  the  rocks  with  unerring  aim  from 
a  considerable  distance.  The  experiments  of  Sir  John 
Lubbock  have  shown  that  the  little  water-flea  (Daphnia)  can 
distinguish  differences  of  colour,  yellows  and  greens  being 
preferred  to  blues  or  reds. 

Among  the  molluscs  there  are  great  differences  in  the 
power  of  sight.  Most  bivalves,  like  the  mussel,  are  blind. 
Interesting  stages  in  the  development  of  the  eye  may  be 
seen  in  such  forms  as  the  limpet,  Trochus  and  Murex.  The 
limpet  has  simply  an  optic  pit,  the  Trochus  a  pit  nearly 
closed  at  the  orifice  and  filled  with  a  vitreous  mass,  and 
the  Murex  a  spherical  organ  completely  closed  in  with  a 
definite  lens.  The  snail  has  a  well-developed  eye  on  the 
hinder  and  longer  horn  or  tentacle.  But  it  does  not  seem 


The  Senses  of  Animals.  293 

to  be  aware  of  the  presence  of  an  object  until  it  is  brought 
within  a  quarter  of  an  inch  or  less  of  the  tentacle.  In  all 
probability  the  eye  does  little  more  than  enable  the  snail 
to  distinguish  between  light  and  dark.  And  the  same  may 
be  said  of  the  eye  of  many  of  the  molluscs.  In  some, 
however,  the  cuttle-fishes  and  their  allies,  the  eye  is  so 
highly  developed  that  it  has  been  compared  with  that  of 
the  vertebrate.  There  is  an  iris  with  a  contractile  pupil. 
And  the  ganglion  with  which  it  is  connected  forms  a  large 
p^art  of  the  so-called  brain.  The  powers  of  accurate  vision 
in  these  higher  forms  are  probably  considerable. 

It  is  interesting  to  note  that  whereas  in  the  cuttle-fishes 
and  most  molluscs,  the  rods  of  the  retina  are  turned 
towards  the  light,  in  Pecten,  Onchidium  (a  kind  of  slug), 
and  some  others,  they  are,  as  in  vertebrates,  turned  from 
the  light.  In  Pecten  the  nerve  to  supply  the  retina  bends 
round  its  edge  at  one  side.  But  in  Onchidium  it  pierces 
the  retina  as  in  vertebrates. 

In  worms,  eyes  are  sometimes  present,  sometimes 
absent.  In  star-fishes  and  their  allies  they  often  occur. 
In  medusse  (jelly-fish)  they  are  sometimes  found  on  the 
margin  of  the  umbrella.  Even  in  lowly  organisms,  like 
the  infusoria,  eye-spots  not  unfrequently  occur.  We  must 
remember,  however,  that,  in  these  lower  forms  of  life,  the 
organs  spoken  of  as  eyes  or  eye-spots  merely  enable  the 
possessor  to  distinguish  light  from  darkness. 

Even  when  eyes  or  eye-spots  are  not  developed,  the 
organism  seems  to  be  in  some  cases  sensitive  to  light — 
using  the  word  "sensitive,"  once  more,  in  its  merely  physical 
acceptation.  The  earthworm,  for  example,  though  it  has 
no  eyes,  is  distinctly  sensitive  to  light ;  and  the  same  has 
been  shown  to  be  the  case  with  other  eyeless  organisms. 
Graber  holds  that  his  experiments  demonstrate  that  the 
eyeless  earthworm  can  distingush  between  different  colours 
— in  other  words,  is  differentially  sensitive  to  light-waves 
of  different  vibration-period — preferring  red  to  blue  or 
green,  and  green  to  blue.  And  the  same  observer  has 
shown  that  animals  provided  with  eyes — the  newt,  for 


294  Animal  Life  and  Intelligence. 

example — can  distinguish  between  light  and  darkness  by 
the  general  surface  of  the  skin.  M.  Dubois,  by  a  number 
of  experiments  on  the  blind  Proteus  of  the  grottoes  of 
Carniola,  has  shown  that  the  sensitiveness  of  its  skin  to 
light  is  about  half  that  of  its  rudimentary  eyes ;  and, 
further,  that  this  sensibility  varies  with  the  colour  of  the 
light  employed,  being  greatest  for  yellow  light.* 

We  have  not  been  able  to  do  more  than  make  a  rapid 
survey  of  the  sense  of  sight  as  it  seems  to  be  developed  in 
the  invertebrates  and  lower  animals.  The  visual  organs 
differ,  not  only  in  structure,  but  in  principle.  We  may,  I 
think,  distinguish  four  types. 

1.  Organs  for  the  mere  appreciation  of  light  or  dark- 
ness (shadow),  exemplified  by  pigment-spots,  with  or  with- 
out concentrating  apparatus. 

2.  Organs  for  the  appreciation  of  the  direction  of  light 
or  shadow,  with  or  without  a  lens.     The  simple  retinal  eyes 
of  gasteropods,  and  perhaps  in  some  cases  the  ocelli  of 
insects,  probably  belong  to  this  class. 

3.  True  eyes,  or  organs  in  which  a  retinal  image  is 
formed,   through  the    instrumentality  of    a  lens,   as  in 
vertebrates  and  cephalopods. 

4.  The  facetted  eyes  of  insects,  in  which  a  stippled 
image  is  formed,  on  the  principle  of  mosaic  vision. 

Unfortunately,  all  these  are  called  indiscriminately 
eyes,  or  organs  of  vision.  An  infusorian  or  a  snail  is  said 
to  see.  But  the  terms  "eye,"  "vision,"  "sight,"  imply 
that  final  excellence  to  which  only  the  higher  animals, 
each  on  its  own  line,  have  attained. 

This  final  excellence  probably  has  its  basis  and  earliest 
inception  in  the  fact  that  the  functional  activity  of  proto- 
plasm is  heightened  in  the  presence  of  setherial  vibrations. 
If,  then,  we  imagine,  as  a  starting-point,  a  primitive 
transparent  organism  with  a  general  susceptibility  to  the 
influence  of  light-vibrations,  the  formation  within  its 
tissues  of  pigment-granules  absorbent  of  light  will  render 
the  spots  where  they  occur  specially  sensitive  to  the 
.  *  See  Nature,  vol.  xli.  p.  407. 


The  Senses  of  Animals.  295 

aetherial  vibrations.  Special  refraction-globules  would  also 
act  as  minute  lenses,  focussing  the  light,  and  thus  concen- 
trating it  upon  certain  spots. 

In  many  of  the  lower  animals  we  find  such  organs, 
belonging  to  our  first  category,  and  constituting  either  eye- 
spots  of  pigmented  material  or  simple  lenses  covering  a 
pigmented  area.  If  we  call  these  eyes,  we  must  remember 
that  in  all  probability  they  have  no  power  of  what  we  call 
vision — only  a  power  of  distinguishing  light  from  dark. 
Where,  however,  there  exists  beneath  the  lens  a  so-called 
retina,  that  is,"  a  layer  of  rod-like  endings  of  a  nerve,  it 
might,  at  first  sight,  be  thought  that  there,  at  any  rate,  we 
have  true  vision.  But  in  all  probability,  in  a  great  number 
of  cases  the  retinal  rods  are  simply  for  the  purpose  of 
rendering  the  organism  sensitive,  not  only  to  the  presence 
of  light,  but  to  its  direction.  Light  straight  ahead  (a)  stimu- 
lates the  middle  rods  ;  from  one  side  (b,  c)  it  is  focussed  on 
the  rods  of  the  opposite  side  of 
the  retina  ;  and  similarly  for 
intermediate  positions.  The 
presence  of  a  retinal  layer  is 
thus  no  infallible  sign  of  a 
power  of  vision  as  apart  from 
mere  sensibility  to  light.  In- 
deed, in  a  great  number  of  c 

'  .,  ,  Fig.  39.— Direction-retina. 

cases,  from  the  convexity  and  Simple  retina  for  distinguishing  the  direction 
position  of  the  lens,  the  for- 
mation of  an  image  is  impossible.  Only  when  it  can  be 
shown  that  a  more  or  less  definite  image  can  be  focussed 
on  the  retina,  or  can  be  formed  on  the  principle  of  mosaic 
vision,  can  we  justly  surmise  that  a  power  of  true  vision 
is  present.  I  doubt  whether  this  can  be  shown  to  be 
unquestionably  the  case  in  any  forms  but  the  higher 
arthropods,  the  cuttle-fishes  and  their  allies,  and  the  verte- 
brates. 

There  is  one  more  point  for  consideration  before  we 
leave  the  sense  of  sight— Are  the  limits  of  vision  the  same 
in  the  lower  forms  of  life  as  they  are  in  man  ?  or,  to  put 


296  Animal  Life  and  Intelligence. 

the  question  in  a  more  satisfactory  form — Are  the  limits 
of  sensibility  to  light- vibrations  the  same  in  them  as  in  us? 
M.  Paul  Bert  concluded  that  they  are.  But  Sir  John 
Lubbock  has,  I  think,  conclusively  shown  that  they  are 
not.  For  the  full  evidence  the  reader  is  referred  to  his 
"  Senses  of  Animals."  *  His  experiments  on  ants,  with 
which  those  of  M.  Forel  are  in  complete  accordance, 
satisfied  him  that  these  little  animals  are  sensitive  to  the 
ultra-violet  rays  which  lie  beyond  the  range  of  our  vision. 
Other  experiments  with  fresh-water  fleas  (Daphnia)  showed 
that  they  have  colour-preferences,  green  and  yellow  being 
the  favourite  colours. 

The  daphnias  were  placed,  in  a  shallow  wooden  trough, 
divided  by  movable  partitions  of  glass  into  divisions. 
Over  this  was  thrown  a  spectrum  of  rainbow  colours.  The 
partitions  were  removed,  and  the  daphnias  allowed  to 
collect  in  the  differently  illuminated  parts  of  the  trough. 
The  partitions  were  then  inserted,  and  the  number  of 
crustaceans  in  each  division  counted.  The  following 
numbers  resulted  from  five  such  experiments  : — 

Dark.       Violet.        Blue.         Green.        Yellow.         Bed. 
0  3  18  170  36  23 

Special  experiments  seem  to  show  that  their  limits  of 
vision  at  the  red  end  of  the  spectrum  coincide  approxi- 
mately with  ours ;  but  at  the  violet  end  their  spectrum  is 
longer  than  ours.  Sir  John  covered  up  the  visible  spectrum, 
Rr>  as  to  render  it  dark,  and  gave  the  daphnias  the  option 
of  collecting  in  this  dark  space  or  in  the  ultra-violet.  To 
human  eyes  both  were  alike  dark.  But  not  so  to  the 
daphnian  eye ;  for  while  only  14  collected  in  the  covered 
part,  286  were  found  in  the  ultra-violet.  The  width  of  the 
violet  visible  to  man  was  two  inches.  Sir  John  divided 
the  ultra-violet  into  three  spaces  of  two  inches  each.  Of 
the  286  daphnias,  261  were  in  the  space  nearest  the  violet, 
25  in  the  next  space,  and  none  in  the  furthest  of  the  three 
spaces.  From  which  it  would  seem  that,  though  these 
little  creatures  are  sensitive  to  light  of  higher  vibration- 

*  Chap.  x.  p.  202. 


The  Senses  of  Animals. 


297 


period  than  that  which  affects  the  human  eye,  their  limits 
do  not  very  far  exceed  ours.  We  have  seen  that  human 
beings  differ  not  a  little  in.  their  limits  of  violet-sus- 
ceptibility. We  may  presume  that  Sir  John  Lubbock 
and  those  who  assisted  him  in  these  experiments  were 
normal  in  this  respect.  But  it  is  possible  that  some  indi- 
viduals could  have  perceived  a  faint  purple  where  there 
was  darkness  to  them,  and  that  the  majority  of  the  261 
daphnias  were  collected  in  the  region  just  beyond  the 
partition  between  ultra-violet  and  darkened  violet.  Still, 
there  is  no  cause  for  doubting  the  general  conclusion  that 
daphnias  are  sensible  to  ultra-violet  rays  beyond  the  limits 
of  human  vision. 


Sir  John  Lubbock  has  an  interesting  chapter  on  pro- 
blematical organs  of  sense.     In  the  antennae  of  ants  and 


Fig.  40.— Antennary  structures  of  hymenoptera.     (After  Lubbock.) 

a.,  cuticle;  b.,  hypodf-rmls;  c.,  ordinary  hair;  d.,  tactile  hair;  e.,  cone;  /.,  depressed 
hair  lying  over  a.  cup  with  rudimentary  hair  at  the  base;  &.,  simple  cup;  t.,  champagne- 
cork-like  organ  of  Forel ;  k.,  flask-like  organ ;  Z.,  papilla,  with  a  rudimentary  hair  at  the  apex. 

bees  there  are  modified  hairs  and  pits  in  the  integument 
(at  least  eight  different  types,  according  to  Sir  John 
Lubbock),  the  sensory  nature  of  which  is  undoubted.  But 
what  the  sensory  nature  in  each  case  may  be  is  more  or 
less  problematical.  Many  worms  have  sense-hairs  or 
bristles  of  the  use  of  which  we  are  ignorant.  Some  organs 


298  Animal  Life  and  Intelligence. 

described  as  tactile  or  olfactory  in  the  lower  invertebrates 
are  so  described  on  a  somewhat  slender  basis  of  evidence. 
The  sense-value  of  the  bright  marginal  beads  of  sea- 
anemones  is  unknown.  Even  in  animals  as  high  in  the 
scale  of  life  as  fishes,  there  is  a  complete  set  of  sense- 
organs — the  muciparous  canals,  in  the  head  and  along  the 
lateral  line  down  the  side,  the  function  of  which  we  can 
only  guess.  By  some  they  are  regarded  as  olfactory ;  by 
others,  as  fitted  to  respond  to  vibrations  or  shocks  of 
greater  wave-length  than  the  auditory  organ  can  appre- 
ciate ;  by  others,  as  of  importance  for  the  equilibration  or 
balancing  of  the  fish. 

It  will  thus  be  seen  that,  apart  from  the  possibility  of 
unknown  receptive  organs  as  completely  hidden  from 
anatomical  and  microscopic  scrutiny  as  the  end-organs  of 
our  temperature-sense,  there  are  in  the  lower  animals 
organs  which  may  be  fitted  to  receive  modes  of  influence 
to  which  we  human  folk  are  not  attuned. 

And  what  are  the  physical  possibilities  ?  We  have  seen 
that,  through  the  telaesthetic  senses — hearing,  vision,  and 
the  temperature-sense — we  are  made  aware  of  the  vibra- 
tions of  distant  bodies,  the  effects  of  which  are  borne  to  us 
on  waves  of  air  or  of  aether.  The  limits  of  hearing  with  us 
are  between  thirty  and  about  forty  thousand  (or  perhaps, 
in  very  rare  cases,  fifty  thousand)  vibrations  per  second. 
But  these  are  by  no  means  the  limits  of  vibrations  of  the 
same  class.  By  experiments  with  sensitive  flames,*  Lord 
Rayleigh  has  detected  vibrations  of  fifty- six  thousand  per 
second ;  and  Mr.  W.  F.  Barrett  has  shown  that  a  sen- 
sitive flame  two  feet  long  is  sensitive  to  vibrations  beyond 
the  limit  of  his  own  hearing  and  that  of  several  of  his 
friends  who  were  present  at  the  experiment.  We  have 
some  reason  to  suppose  that  vibrations  too  rapid  to  be 
audible  by  man  are  audible  by  insects,  but  not  much  is 
known  with  regard  to  the  exact  limits. 

The  following  table  shows  what  is  known  concerning 

*  The  observations  are  not  yet  published,  and  I  have  to  thank  Lord 
Rayleigh  for  his  courtesy  in  allowing  me  to  make  use  of  this  fact. 


The  Senses  of  Animals. 


299 


the  aBther-vibrations.      The  figures    are  those    given  by 
Professor  Langley  : — 


Quality  of  radiations. 

Limit  of  photography,  arti- 
ficial source 

Limit  of  photography,  solar 
source 

Limit  of  violet  to  normal 

eyes          

Limit  of  red  to  normal  eyes 
Probable   inferior   limit   of 
temperature-sensations . . 
Longest  waves  hitherto  re- 
cognized with  bolometer 


Wave-lengths  in  Number  of 
thousandths  of  vibrations  pel 
a  millimetre,  second  in  billio 


0-185 
0-295 


0-36 
0-81 


9-25* 
30-0 


160 


833) 
370  \ 

30 
1 


none  known 


vision. 

temperature- 

sense 
none  known 


From  this  table  it  will  be  seen  that,  apart  from  the 
possible  extension  of  sight  beyond  human  limits,  there  are 
possibilities  of  another  sense  for  the  ultra-violet  actinic 
vibrations  as  different  from  sight  as  is  the  infra-red 
temperature-sense.  Moreover,  the  temperature-sense  for 
us  has  no  scale ;  there  is  nothing  corresponding  to  pitch 
in  sound  or  colour  in  sight.  It  may  not  be  so  with  lower 
organisms.  Insects,  for  example,  may  be  sensitive  to  tones 
of  heat.  The  bee  may  enjoy  a  symphony  of  solar  radiance. 

I  am  not  saying  that  it  is  so;   I  am  merely  suggesting 
possibilities  which  we  have  not   sufficient  knowledge  to 
authoritatively  deny.      We  have  no  right  to  impose  the 
limits  of  human  sensation  on  the  entire  organic  world. 
Insects  may  have  "  permanent  possibilities  of  sensation  " 
denied  to  us. 

Even  within  our  limits  there  may  be,  as  we  have 
already  seen,  great  and  inconceivable  differences.  We  saw 

*  Professor  Langley  finds  that  the  maximum  effect  with  a  radiating 
source  at  170°  C.  is  at  about  5-0  thousandths  of  a  millimetre  wave-length. 
„       100°  C.      „      „      7-5 
0°C.      „      „    11-0 

We  are  sensitive  to  radiations  from  a  body  at  100°  C.  But  when  the 
temperature  falls  below  the  normal  temperature  of  the  body  we  are  not 
sensitive  to  heat-vibrations,  but  to  loss  of  heat  from  the  surface  exposed.  The 
limit  of  sensibility  to  heat-vibrations,  therefore,  probably  lies  between  7'5  and 

II  thousandths  of  a  millimetre.      I  have  taken  about  9-25  as  the  limit. 


300  Animal  Life  and  Intelligence. 

that  our  own  colour-sensations  are  probably  due  to  the 
blending  and  overlapping  in  different  proportions  of  three 
primitive  monochromatic  bands,  but  that  in  all  probability 
in  birds  the  bands  are  different,  and  overlapping  is  largely 
prevented.  Their  colour-phenomena  must  be  inconceivably 
different  from  ours.  And  what  shall  we  say  of  the  colour- 
vision  of  invertebrates  ?  Are  we  justified  in  supposing  that 
for  them,  as  for  us,  E.,  G.,  and  V.  are  the  unstable  ex- 
plosives, and  that  they  are  present  in  the  same  proportions 
as  with  us  ?  If  not,  their  colour-world  cannot  be  the  same 
as  ours.  Of  the  same  order  it  probably  is.  And  all  that 
we  can  hope  to  do  is  to  show,  as  has  been  shown,  that 
colours  which  differently  affect  us  affect  them  also 
differently. 

In  conclusion,  we  may  return  to  the  point  from  which 
we  set  out.  The  organism  is  fitted  to  respond  to  certain 
influences  of  the  external  world.  The  organs  for  the 
reception  of  these  influences  are  the  sense-organs.  When 
they  are  stimulated  waves  of  change  are  transmitted 
inwards  to  the  great  nerve-centres;  they  are  there  co- 
ordinated, and  issue  thence  to  muscles  or  glands.  Thus  the 
organism  is  fitted  to  respond  to  the  influences  from  without. 
The  activities  of  organisms  are  in  response  to  stimulation. 

We  have  seen  that  the  cells  of  the  organic  tissues  are 
like  little  packets  of  explosives,  and  that  the  changes  which 
occur  in  the  organism  may  be  likened  to  their  explosion 
and  the  setting  free  of  the  energy  stored  up  in  them.  The 
end-organs  of  the  special  senses  may  be  regarded  as 
charged  with  explosives  of  extreme  sensitiveness.  Some 
are  fired  by  a  touch ;  the  molecular  vibrations  of  sapid  or 
odorous  particles  explode  others ;  yet  others  are  fired  by 
the  coarser  vibrations  of  sound ;  others,  once  more,  by  the 
energy  of  the  aetherial  waves.  The  visual  purple  is  a  highly 
unstable  chemical  compound  of  this  kind  ;  expose  it  for  a 
moment  to  light,  and  it  topples  over  to  a  new  molecular 
arrangement,  the  colour  being  at  the  same  time  discharged. 
If  the  retina  has  been  removed  from  the  body,  this  is  all 


The  Senses  of  Animals.  301 

that  happens.  But  if  (in  the  frog)  it  be  replaced  on  the 
choroid  layer  from  which  it  has  been  stripped,  the  visual 
purple  is  reformed.  The  explosive  is  thus  reconstructed 
and  the  sensibility  is  restored.  Thus,  as  fast  as  the 
explosives  are  fired  off  by  sense-stimuli,  so  fast  in  normal 
life  are  they  reconstituted  and  the  sensibility  restored. 
Meanwhile  the  explosion  at  the  end-organs  has  fired  the 
train  of  explosives  in  the  nerve,  and  created  molecular 
explosive  disturbances  in  the  brain.  Thence  the  explosive 
waves  pass  down  other  nerves  to  muscles  or  glands,  and, 
giving  rise  therein  to  further  explosions,  take  effect  in  the 
activities  of  the  organism. 

We  shall  have  to  consider  these  activities  hereafter. 
We  must  now  turn  to  the  psychical  or  mental  accom- 
paniments of  the  explosive  disturbances  in  the  brain  or 
other  aggregated  mass  of  nerve-cells. 


302  Animal  Life  and  Intelligence. 


CHAPTER  VIII. 

MENTAL   PROCESSES    IN   MAN. 

I  HAVE  already  drawn  attention  to  the  fact  that  the  primary 
end  and  object  of  the  reception  of  the  influences  (stimuli) 
of  the  external  world,  or  environment,  is  to  enable  the 
organism  to  answer  or  respond  to  these  special  modes  of 
influence,  or  stimuli.  In  other  words,  their  purpose  is  to 
set  agoing  certain  activities.  Now,  in  the  unicellular 
organism,  where  both  the  reception  and  the  response  are 
effected  by  one  and  the  same  cell,  the  activities  are  for 
the  most  part  simple,  though  even  among  these  protozoa 
there  are  some  which  show  no  little  complexity  of  response. 
Where,  however,  the  organism  is  composed  of  a  number  of 
cells,  in  which  a  differentiation  of  structure  and  a  specializa- 
tion of  function  have  been  effected,  certain  cells  are  set 
apart  as  recipients,  while  other  cells  are  set  apart  to 
respond  (respondents).  There  is  thus  the  necessity  of  a 
channel  of  communication  between  the  two.  Hence  yet 
other  cells  (transmitters),  arranged  end  to  end,  form  a  line 
of  connection  and  communication  between  the  group  of 
receiving  cells  and  the  group  of  responding  cells,  and  con- 
stitute what  we  term  a  nerve.  That  which  is  transmitted 
may  still  be  called  a  stimulus,  each  cell  being  stimulated 
in  turn  by  its  neighbour.  Thus  a  stimulus  must  be  first 
received  and  then  transmitted. 

But  little  observation  is  required  to  convince  us  of  the 
fact  that,  in  ifche  higher  creatures,  a  very  simple  stimulus 
may  give  rise  to  a  very  complex  response.  A  light  pin- 
prick will  cause  a  vigorous  leap  in  a  healthy  frog — a  leap 
that  involves  a  most  intricate,  accurate,  and  complex 


Mental  Processes  in  Man.  303 

co-ordination  of  muscular  activities.  And  anatomical 
investigation  shows  us  that  in  such  creatures  there  is 
always,  in  the  course  of  the  channel  of  communication  or 
transmission,  a  group  of  closely  connected  cells,  which 
play  the  part  of  co-ordinants.  In  the  vertebrate  animals 
these  co-ordinants  are  collected  in  the  brain  and  spinal 
cord.  In  the  insects,  crustaceans,  and  worms  they  are 
arranged  in  a  knotted  chain  running  close  to  the  under 
surface  of  the  body.  To  this  central  nervous  system,  as  it 
is  called,  nerves  (afferent  nerves)  run  inwards  from  the 
recipient  organs.  From  it  nerves  (efferent  nerves)  run 
outwards  to  the  organs  of  response.  And  in  it  the  trans- 
mitted stimuli,  brought  in  by  the  afferent  nerves,  are 
modified,  through  intervention  of  the  co-ordinants,  into 
stimuli  carried  out  by  the  efferent  nerves.  A  simple 
stimulus  may  create  a  great  commotion  among  the  co- 
ordinants  of  the  central  nervous  system,  and  give  rise  to 
many  and  complex  stimuli  going  out  to  the  muscles  and 
other  organs  of  response.  How  this  is  effected  is  one  of 
the  many  wonders  of  the  animal  mechanism.  We  believe 
that  the  connection  and  co-ordinations  have  gradually  been 
established  during  a  long  process  of  development  and  evo- 
lution, reaching  back  far  into  the  past.  How,  we  can  at 
present  scarcely  guess. 

We  must  picture  to  ourselves,  then,  in  the  animal 
organism,  a  multitude  of  nerve-fibres  running  inwards 
from  all  the  end-organs  of  the  special  senses,  from  the 
muscles,  and  from  the  internal  organs,  and  all  converging 
on  the  central  nervous  system.  And  we  must  picture  to 
ourselves  a  multitude  of  nerve-fibres  passing  outwards  from 
the  central  system,  and  diverging  to  supply  the  muscles, 
glands,  and  other  organs  which  are  to  respond  to  the 
stimulation  from  without.  We  must  picture  the  fibres 
coming  from  or  going  to  related  parts  or  organs  collecting 
together  to  form  nerves  and  nerve-trunks,  which  are, 
however,  only  bundles  of  isolated  nerve-fibres.  And, 
lastly,  we  must  picture  the  central  nerve-system  itself 
co-ordinating  and  organizing  the  stimuli  brought  into  it 


304  Animal  Life  and  Intelligence. 

by  afferent  nerves,  from  the  organs  of  special  sense,  and 
handing  over  the  resultants  by  efferent  nerves  to  the 
organs  of  special  activities.  So  far  we  have  purely 
physiological  effects,  many  of  which  occur  with  surprising 
accuracy  and  precision  when  an  organism  is  in  a  state  of 
unconsciousness.  Place  your  finger  in  the  palm  of  a 
sleeping  child,  and  the  fingers  will  close  over  it  without 
the  child  awaking  to  consciousness.  If,  in  a  frog,  the 
brain  of  which  has  been  extirpated,  the  side  be  touched 
with  a  drop  of  acid,  the  leg  of  that  side  will  be  drawn  up, 
and  the  foot  will  be  used  to  wipe  away  the  acid.  And  if 
that  leg  be  held  and  prevented  from  reaching  the  side,  the 
other  leg  will  be  brought  round  so  as  to  try  and  bring  the 
foot  within  reach  of  the  irritated  spot.  The  actions  are, 
however,  in  all  probability,  purely  physiological,  and  are 
performed  in  complete  absence  of  consciousness. 

When  we  turn  from  the  physiological  to  the  psycho- 
logical aspect  of  the  question,  we  enter  a  new  world,  the 
world  of  consciousness,  wherein  the  impressions  received 
by  the  recipient  organs  (no  longer  regarded  as  mere  stimuli, 
but  as  the  elements  of  consciousness)  are  co-ordinated  and 
organized,  and  are  built  up  into  those  sensations  and 
perceptions  through  which  the  objects  of  the  external 
world  take  origin  and  shape.  It  is  with  this  process  that 
we  have  now  to  deal;  and  we  will  deal  with  it  first  in 
man. 

The  first  fact  to  notice  is  that,  apart  from  sense-stimuli 
received  and  exciting  consciousness,  we  have  also  the 
revival  of  past  impressions.  This  revival  is  the  germ  of 
memory.  What  exactly  is  the  physical  basis  of  memory, 
how  the  effects  of  stimuli  in  consciousness  come  to  be 
registered,  we  do  not  know.  It  is  clearly  a  matter  that 
falls  under  the  general  law  of  persistence ;  but  in  what 
organic  manner  we  are  largely  ignorant.  Still,  there  can 
be  no  question  of  the  fact  that,  quite  apart  from  impres- 
sions due  to  immediate  influences  of  the  environment  now 
acting  on  our  recipient  organs,  we  have  also  revivals  of 


Mental  Processes  in  Man.  305 

bygone  influences  of  the  environment — shadows  or  after- 
images of  previous  modes  of  influence.  Without  this 
process  of  registration  and  revival,  stimuli  could  never 
give  rise  to  sensations  and  perceptions  such  as  we  know 
them.  Without  it  experience  would  be  impossible. 

We  may  say,  then,  that  impressions  (resulting  from 
stimuli)  and  their  revival  in  memory  are  the  bricks  of  the 
house  of  knowledge ;  and  these'  are  built  up  through  ex- 
perience into  what  we  call  the  world  of  things  around 
us.  There  may  be  and  is  a  certain  amount  of  mortar, 
supplied  by  the  builder,  in  addition  to  the  elementary 
bricks.  But  without  the  bricks  no  house  of  knowledge 
could  be  built.  Let  us  now  examine  the  bricks  and  the 
building. 

From  what  we  have  already  learnt  in  the  chapter  on 
"  The  Senses  of  Animals,"  it  is  clear  that  the  impressions 
and  their  revivals  in  memory  have  differences  in  quality. 
Here,  on  the  very  threshold  of  the  subject,  we  must  pause. 
They  have  differences  of  quality.  But  in  consciousness 
these  differences  must  be  distinguished.  And  this  involves 
their  recognition  and  discrimination,  presupposing,  there- 
fore, a  corresponding  faculty,  however  simple,  on  the  part 
of  the  recipient.  Without  cognition  and  recognition  (twin 
sisters,  born  in  the  same  hour)  we  can  never  get  beyond 
mere  impressions;  which  may,  indeed,  be  differentiated 
physically,  as  different  stimuli  due  to  diverse  action  of  the 
environment,  but  are  psychically  undifferentiated.  This 
recognition  and  discrimination  is  thus  the  primary  activity 
of  the  recipient  mind.  Here  is  already  some  of  the  mortar 
supplied  by  the  builder.  Memory  is  absolutely  essential  to 
the  process.  The  sense-impression  of  external  origin  gives 
rise  to  an  impression  of  similarity  or  dissimilarity,  which  is 
part  of  the  internal  reaction  to  the  external  stimulus. 
Thus  impressions  are  raised  to  the  level  of  sensations.  A 
sensation  is  an  impression  that  has  been  discriminated 
from  others,  and  recognized  as  being  of  such  and  such  a 
nature.  The  impressions  of  the  sense-organs  as  we  know 
them  are  thus  not  mere  impressions,  but  impressions 

x 


306  Animal  Life  and  Intelligence. 

raised  to  the  level  of  sensations,  in  so  far  as  they  are 
recognized  and  discriminated. 

Let  us  now  glance  at  some  of  the  differences  in  quality 
recognized  in  sensation.  First,  we  have  the  broadly  dis- 
tinguished groups  of  touches  and  pressures,  temperature- 
sensations,  tastes,  smells,  sounds,  sights,  muscular  sensa- 
tions, and  organic  sensations  from  internal  parts  of  the 
body.  And  then,  within  each  of  these  groups,  there  are 
the  more  or  less  delicate  and  distinct  shades  of  quality, 
well  exemplified  in  vision  by  the  different  colour-sensations, 
in  hearing  by  notes  of  different  pitch,  and  in  smell  by  the 
varieties  of  scents  and  odours.  Many  of  those  sensations, 
moreover,  which  are  apparently  simple,  are  in  reality 
compound.  There  are  differences  of  quality  in  the  note  A 
as  sounded  on  a  violin,  a  piano,  and  a  flute ;  and  these 
differences  are  due  to  different  admixtures  of  overtones, 
which  fuse  with  the  fundamental  tone  and  alter  its  timbre. 
So,  too,  with  vision.  The  sensation  given  by  a  white  disc 
is  a  compound  sensation,  due  to  waves  of  different  period, 
which  separately  would  give  sensations  of  colour.  Sensa- 
tions, then,  differ  in  quality. 

They  also  differ  in  quantity  or  intensity.  This  needs 
little  illustration.  As  evening  falls,  the  sight-sensations 
derived  from  the  surrounding  objects  grow  more  and  more 
feeble.  They  may  remain  the  same  in  quality,  but  the 
quantity  or  intensity  gradually  diminishes.  So,  too,  in 
music,  the  pianos  and  fortes  give  us  differences  in  intensity 
of  sound-sensations. 

Sensations  also  differ  in  duration.  The  stimulation 
may  be  either  prolonged  or  instantaneous.  Two  or  more 
sensations  may,  moreover,  be  simultaneous  or  successive. 
Just  as  they  may  be  either  similar  or  different  in  quality 
and  in  intensity,  so  they  may  be  either  simultaneous  or 
successive  in  time.  Simultaneous  sensations  are  best 
exemplified  in  vision  and  through  touch ;  successive  sensa- 
tions are  given  most  clearly  by  the  sense  of  hearing, 
through  which  we  recognize  a  sequence  of  sounds. 

And  then,  again,  sensations  not  only  differ  in  time,  but 


Mental  Processes  in  Man.  307 

they  seem  also  to  differ  in  place.  A  sensation  of  touch 
may  be  referred  to  different  parts  of  the  body — the  hand, 
the  foot,  or  the  forehead.  But  here  we  open  up  an  im- 
portant question — Where  do  we  feel  a  sensation,  such  as, 
for  example,  that  of  pressure  on  the  skin  ?  Common  sense 
answers,  without  hesitation,  that  we  feel  it  at  the  particular 
part  of  the  body  which  is  affected  by  the  external  stimulus. 
I  feel  the  pen  with  which  I  write  with  my  finger-tips.  And 
common  sense  is  perfectly  right  from  its  own  point  of 
view.  But  it  is  a  well-known  fact  that  a  person  whose  leg 
has  been  amputated  experiences  at  times  tickling  and 
uneasiness  in  the  absent  member.  This  is  due  to  irritation 
of  the  nerve-ends  in  the  stump  of  the  limb.  But  the 
sensations  are  referred  outwards  to  the  normal  source  of 
origin  of  impressions,  the  effects  of  which  were  carried 
inwards  by  the  nerve  affected.  We  shall  have  to  consider 
hereafter  the  nature  of  the  relation  between  physiological 
and  psychological  processes — the  connection  of  mind  and 
body.  Assuming  for  the  present  that  psychical  processes 
have  a  physical  basis  in  physiological  processes,  the  fact 
given  above  and  others  of  like  implication  seem  to  show 
that  the  sensation  has  for  its  physiological  basis  some 
nerve-change  in  the  central  nervous  system — in  us,  no 
doubt,  in  the  brain.  Of  course,  it  must  be  remembered 
that  the  sensation,  as  felt,  is  a  mental  fact  (using  the  word 
"  mental "  in  its  broadest  sense,  as  belonging  to  the 
psychical  as  opposed  to  the  physiological  series).  But  it 
would  seem  that  the  physiological  accompaniment  of  this 
mental  fact  is  some  nerve-change  in  the  brain.  This 
nerve-change  is  caused  by  a  stimulus  having  its  origin  in 
the  end-organ  of  the  afferent  nerve,  and  we  naturally  refer 
the  impression  outwards  to  the  place  of  its  source  of  origin 
under  ordinary  and  normal  conditions.  In  other  words, 
we  localize  it.  That  is  what  common  sense  means  when  it 
says  that  we  feel  pressure  at  the  finger-tips. 

To  account  for  this  process  of  localization,  it  is  supposed 
that  every  sensation,  apart  from  its  special  quality  as  a 
touch,  a  taste,  or  a  smell,  has  a  more  or  less  defined 


3oB  Animal  Life  and  Intelligence. 

spatial  quality,  or  local  sign,  dependent  upon  the  part  of 
the  body  to  which  the  stimulus  is  applied.  These  local 
signs  have,  doubtless,  in  the  long  run,  been  established  by 
experience — if  under  this  term  we  may  include  a  more  or 
less  unconscious  process,  the  outcome  of  evolution.  But 
they  are  so  rapidly  established  in  the  individual,  that  we 
are  forced  to  conclude  that  we  inherit  very  highly  developed 
aptitudes  for  localization. 

The  refinement  of  localization  is  very  different  in  the 
different  senses.  In  smell  and  taste  there  seems  no  more 
than  a  general  localization  in  the  organ  affected — the  nose 
or  the  mouth.  In  hearing  there  is  not  much  more,  unless 
we  regard  the  discrimination  of  pitch  as  a  mode  of  localiza- 
tion. In  touch  (and  temperature)  the  refinement  is  much 
higher,  but  it  varies  with  the  part  of  the  body  affected. 

If  the  back  be  touched  by  two  points  less  than  two 
inches  and  a  third  apart,  the  sensation  will  be  that  of  a 
single  point ;  the  finger-tips,  however,  can  distinguish  two 
points  separated  by  less  than  one-tenth  of  an  inch ;  and 
the  tip  of  the  tongue  is  still  more  refined  in  its  power  of 
discrimination,  distinguishing  as  two,  points  separated  by 
less  than  the  twenty-fifth  part  of  an  inch.  So  that  the 
tongue  is  about  sixty  times  as  refined  in  its  discrimination 
as  the  skin  of  the  back.  Moreover,  the  delicacy  of  localiza- 
tion may  be  cultivated,  so  that  in  some  cases  the  refine- 
ment may,  by  practice,  be  doubled. 

When  we  come  to  sight,  the  refinement  of  localization 
reaches  its  maximum,  the  local  signs  in  the  retina  showing 
the  highest  stage  of  differentiation,  the  distance  on  the 
retina  between  two  points  distinguishable  by  local  signs 
being,  according  to  Helmholtz,  not  much  more  than  -tflfoT 
of  an  inch  ('0044  millimetre),  which  nearly  corresponds 
with  the  space  between  two  cones  in  the  yellow  spot. 

We  must  remember  that  the  presentations  of  sense  are 
in  all  cases  given  in  a  stippled  form,  that  is,  by  the  stimu- 
lation of  a  number  of  separate  and  distinct  points.  In 
vision  the  stippling  is  very  fine,  owing  to  the  minute  size 
and  close  setting  of  the  retinal  cones.  In  the  case  of 


Mental  Processes  in  Man.  309 

hearing,  the  stippling,  if  we  may  so  extend  the  use  of  this 
term,  is  also  very  fine,  a§  is  shown  by  the  fact  that 
musicians  can,  according  to  Weber,  distinguish  notes 
separated  in  the  scale  of  sounds  by  only  one-sixtieth  part 
of  a  musical  tone.  In  touch  the  stippling  is  comparatively 
coarse.  But  in  all  cases  there  is  a  stippling;  and  yet 
from  these  stippled  sensations  the  mind  in  all  cases  elabo- 
rates a  continuum.  The  visual  image  is  continuous,  not- 
withstanding the  retinal  stippling  and  the  existence  of  the 
blind  spot.  When  we  lay  our  hands  on  a  smooth  table  we 
fill  in  the  interstices  between  the  sensational  points,  and 
feel  the  surface  as  continuous.  In  all  cases  out  of  the 
stippled  sense-stimuli  we  form  a  continuum. 

The  next  thing  that  we  have  to  note  is  that  it  is  not  so 
much  the  sensation  itself,  as  that  which  gives  origin  to 
it,  that  we  habitually  refer  outwards  to  the  recipient  end 
of  the  afferent  fibre.  In  referring  a  sensation  of  touch  to 
a  certain  part  of  the  skin,  it  is  of  something  touching  us 
that  we  seem  to  be  immediately  conscious.  We  refer  the 
stimulus  to  an  object  in  the  external  world,  which  we 
localize,  and  which  we  believe  to  have  given  rise  to  the 
sensation. 

This,  however,  is  more  clearly  seen  in  the  case  of 
vision.  When  we  look  through  the  window  and  see  an 
object  such  as  a  house  before  us,  we  do  not  habitually 
localize  the  sensation  in  a  certain  part  of  the  retina,  but 
we  refer  the  object  to  a  particular  position  more  or  less 
distant  in  the  world  around  us.  This  projection  of  the 
object  outwards  in  a  right  line  from  the  eyes  is  really  a 
marvellous  process,  though  the  wonder  of  it  is  lost  in  its 
familiarity.  It  is  the  outcome  of  the  experience  of  hundreds 
of  generations.  And  the  experience  is  not  gained  through 
vision  alone,  but  through  this  in  combination  with  other 
senses  and  activities.  We  see  an  object,  but  we  have  to 
go  to  it  before  we  can  touch  it.  It  is  not  in  contact  with 
us,  but  distant  from  us.  Its  outness  and  distance  is  a 
matter  of  what  is  termed  the  geometry  of  the  senses ;  and 
this  geometry  has  been  elaborated  through  many  genera- 


310  Animal  Life  and  Intelligence. 

tions  of  organized  beings,  from  data  given  by  sight,  touch, 
and  the  muscular  sense.  It  is.  true  that  I  can  now  estimate 
the  distance  of  the  house  without  going  to  it ;  but  my  eyes 
go  to  it,  and  I  can  feel  them  go.  The  panes  of  my  window 
are  separated  by  iron  bars.  As  I  look  from  them  to  the 
distant  house  and  back  to  them  again,  I  can  feel  my  eyes 
going  from  one  to  the  other.  The  lens  of  the  eye  is 
adjusted  for  near  or  far  distance  by  the  action  of  a  ciliary 
muscle,  through  which  its  anterior  surface  can  be  flattened, 
returning  again  by  its  own  elasticity  to  the  more  convex 
form  when  the  muscle  ceases  to  act.  Each  eye,  moreover, 
is  moved  in  its  orbit  by  six  eye-muscles,  and  in  normal 
vision  the  two  eyes  act  as  one  organ.  For  near  distances 
they  converge ;  for  far  distances  there  is  less  convergence. 
Through  the  muscular  sense,  which  is  here  extraordinarily 
delicate,  we  can  feel  the  amount  of  accommodation  and 
convergence;  and  thus  we  can  feel  the  eyes  going  to  or 
coming  from  a  near  and  a  distant  object.  Of  course,  we 
are  aided  in  judging  or  estimating  distances  by  the  apparent 
size  of  the  object  when  the  real  size  is  known,  by  the 
clearness  of  its  outlines  in  a  slightly  hazy  atmosphere,  and 
so  forth.  But  apart  from  such  judgments,  it  would  pro- 
bably be  impossible  to  perceive  that  an  object  is  near  or 
distant  in  the  absence  of  muscles  of  accommodation  and 
convergence  affording  the  data  of  the  muscular  sense.  Not 
only  the  distance  of  two  objects  from  the  eye,  but  their 
distance  apart,  can  be  measured  by  the  aid  of  the  muscular 
sense  as  we  move  the  eyes  from  one  to  the  other.  And  in 
us  this  is  so  delicate  that,  according  to  Weber,  a  distinct 
muscular  sensation  is  attached  to  a  displacement  of  a 
sensitive  point  of  the  yellow  spot  through  less  than  ^Q^ 
of  an  inch. 

Now,  if  it  be  true  that  the  consciousness  aroused  by 
objects  around  us,  through  sensation,  is  an  accompaniment 
of  certain  physiological  changes  in  the  brain,  it  is  clear 
that  the  localization  of  their  points  of  origin  in  special 
parts  of  the  skin,  and  the  outward  projection  of  the  objects 
exciting  vision,  is  an  act  of  the  mind  quite  distinct  from 


Mental  Processes  in  Man.  3 1 1 

the  mere  passive  response  in  consciousness  which  we  call 
an  impression,  and  more  complex  than  that  mental  activity 
which,  through  discrimination  and  recognition,  converts  the 
bare  impression  into  a  sensation.  It  is,  in  fact,  part  of 
that  mental  process  which  is  called  perception.*  Sensa- 
tion has  nothing  to  do  with  the  objects  around  us  as  such  ; 
it  is  by  perception  that  we  are  aware  of  their  existence. 
Let  us  now  follow  the  process  of  perception  a  little  further, 
always  remembering  that  it  involves  certain  activities  of 
the  mind. 

These  activities  are  too  often  ignored.  We  often  speak 
of  the  senses  as  the  avenues .  of  knowledge,  and  John 
Bunyan,  likening  the  soul  to  a  citadel,  spoke  of  the  five 
gateways  of  knowledge,  Eye-gate,  Ear-gate,  Mouth-gate, 
Smell-gate,  and  Feel-gate.  Hence  arises  a  vague  notion 
that  through  the  eye-gate,  for  example,  a  sort  of  picture 
of  the  external  object  somehow  enters  the  mind.  And  this 
idea  is  no  doubt  fostered  by  the  fact  that  an  inverted  image 
of  the  object  is  formed  on  the  retina,  though  how  the 
inverted  image  is  turned  right  way  up  again  in  passing 
into  the  mind  bothers  some  people  not  a  little.f 

*  I  use  this  term  in  a  broad  sense,  as  the  process  involved  in  the  formation 
of  what  I  shall  term  constructs. 

t  And  I  may  add  it  is  not  an  easy  matter  to  explain  to  those  who  have  not 
considered  such  questions.  It  is  a  matter  of  the  correlation  of  the  testimony 
of  the  sense-organs.  A  boy  stands  before  me.  I  go  to  him  and  touch  him, 
and  pass  my  hands  downwards  from  head  to  foot.  Then  I  stand  a  little  way 
off  and  look  at  him.  His  image  on  my  retina  is  inverted.  But  as  I  run  my 
eye  over  him  I  direct  my  eye  downwards  to  his  feet  and  upwards  to  his  head. 
I  am  not  conscious  that  the  stimuli  are  running  upwards  along  the  retinal  image. 
Thus  my  eye-muscles  and  my  other  muscular  and  tactile  sensations  seem  to  tell 
me  that  he  is  one  way  upwards.  The  image  on  my  retina  tells  me,,  though  I  am 
not  conscious  of  the  fact,,  that  he  is  the  other  way  upwards.  But  he  cannot 
be  both  !  The  testimony  of  one  sense  has  to  give  way.  One  standard  or  the 
other  has  to  be  adopted.  Practically  that  of  touch  and  the  muscular  sensations 
is  unconsciously  selected,  and  sight-sensations  are  habitually  interpreted  in 
terms  of  this  standard.  So  long  as  the  two  are  sufficiently  accurately 
correlated,  the  practical  requirements  of  the  case  are  met.  And  it  is  well 
known  that  it  is  not  difficult,  with  a  little  practice,  to  establish  a  new  correlation. 
This  is  indeed  done  every  day  by  the  microscopist,  for  whom  the  images  are 
all  reversed  by  his  instrument.  He  very  soon  learns,  however,  that  to  move 
the  object,  as  seen,  to  the  left,  he  must  push  it  to  the  right.  A  new  correlation 
is  rapidly  and  correctly  established. 


312  Animal  Life  and  Intelligence. 

A  much  closer  analogy  is  this :  Something  stands 
without  and  knocks  at  the  doorway  of  sense,  and  from  the 
nature  of  the  knocks  we  learn  somewhat  concerning  that 
which  knocks.  In  other  words,  at  the  bidding  of  certain 
stimuli  from  without  we  construct  that  mental  product 
which  we  call  the  object  of  sense.  It  is  of  these  mental 
constructions — "  constructs "  *  I  will  call  them  for  con- 
venience— that  I  have  now  to  speak. 

In  a  fruiterer's  shop  on  the  opposite  side  of  a  street  I 
see  an  orange.  That  is  to  say,  certain  cones  of  the  retina 
of  my  eye  are  stimulated  by  light-waves  of  a  yellow  quality, 
and  at  the  bidding  of  these  stimuli  I  construct  the  object 
which  I  call  an  orange.  That  object  is  distant,  roundish, 
yellow,  resisting  and  yet  somewhat  soft,  with  a  peculiar 
smell,  and  possessed  of  a  taste  of  its  own.  Now,  it  is 
obvious  that  I  cannot  see  all  these  qualities  of  the  orange, 
as  we  call  them.  I  construct  the  object  on  reception  of 
certain  light-waves  which  are  focussed  on  the  retina  of  my 
eye.  If  I  go  to  the  orange,  however,  I  can  test  the  correct- 
ness of  my  construct  by  the  senses  of  touch,  smell,  and 
taste.  But  what  led  me  to  construct  an  object  with  these 
qualities  ?  Experience  has  taught  me  that  these  qualities 
are  grouped  together  in  special  ways  in  an  orange.  I 
constructed  that  particular  object  through  what  is  termed 
the  principle  of  association.  I  have  learnt  that  these 
qualities  are  grouped  together  in  certain  relations  to  each 
other,  and  when  I  actually  receive  sight-stimuli  of  a  certain 
quality,  grouped  in  certain  ways,  they  immediately  call  up 
the  memories  of  the  associated  qualities.  That  which  is 
actually  received  is  a  mere  suggestion,  the  rest  is  sug- 
gested in  memory  through  association.  The  object  might 
be  suggested  through  other  senses.  I  come  into  a  dining- 
room  after  dessert,  and  the  object  is  suggested  through 
smell.  Or  my  little  son  says,  "  Open  your  mouth  and 
shut  your  eyes,  and  see  what  the  fairies  will  send  you  ;  " 
and  an  orange  is  suggested  by  taste.  In  all  these  cases 

*  I  nse  tins  term  because  the  word  "  percept "  is  used  in  different  senses  by 
different  writers,  e.g.  by  Mr.  Mivart  and  Mr.  Romanes. 


Mental  Processes  in  Man.  313 

the  object  is  constructed  at  the  bidding  of  certain  sensa- 
tions, which  suggest  to  my  mind  the  associated  qualities. 
The  object  is  a  construct. 

And  here  let  us  notice  that  we  ascribe  the  form,  the 
resistance,  the  taste,  the  smell,  to  the  object.  We  do  not 
say  or  think,  "  Sight-sensations  inform  me  that  there  is 
something  which  I  call  an  orange,  and  which  is  capable  of 
exciting  in  me  sensations  of  touch,  taste,  and  smell ;  "  but  we 
say,  "  There  is  an  orange,  which  has  such  and  such  a  taste, 
smell,  and  feel."  In  other  words,  we  refer  these  sensations, 
related  in  certain  ways,  outwards  to  the  object,  and  name 
them  qualities  of  the  object  that  we  see.  But  remember, 
that  we  do  not  necessarily  or  normally  say  or  think  any- 
thing about  it.  We  just  inevitably  construct  the  object, 
what  we  build  in  to  the  construct  depending  upon  associa- 
tion through  experience. 

At  this  stage,  perhaps,  Common  Sense  steps  in,  and, 
shaking  his  head,  says,  with  characteristic  bluntness, 
"  Nonsense ;  you'll  never  persuade  me  that  the  things  I 
see  and  feel  around  me  are  nothing  but  fictions  of  my  own 
mind.  I  don't  construct  them,  as  you  call  it ;  there  they 
are  for  me  to  see  and  feel  and  taste  if  I  will."  Now, 
Common  Sense  is  a  sturdy,  hard-headed  individual,  with 
whom  I  desire  to  keep  on  friendly  terms.  And  I  therefore 
hasten  to  explain  that  I  most  fully  agree  with  every  word 
that  he  says.  The  orange  that  I  see  before  me  is  not  a 
mere  fiction  of  my  mind.  I  can,  if  I  will,  take  it  up,  feel 
it,  smell  it,  and  taste  it.  If  it  will  satisfy  Common  Sense, 
I  will  say  that  it  is  the  idea  of  the  orange  that  I  construct. 
Only  I  think  that  Common  Sense,  who  has  a  horror  of 
roundabout  and  indirect  statements,  will  not  like  my  say- 
ing, "  I  am  receiving  certain  visual  sensations  related  in 
certain  ways,  which  lead  me  to  construct  an  idea  of  an 
orange."  He  will  prefer  my  saying  simply,  "I  see  an 
orange."  Since  what  he  wants  me  to  call  our  ideas  of  things 
answer  point  for  point  to  the  things  as  they  actually  exist 
for  us  human-folk,  it  is  not  only  more  satisfactory  but  more 
correct  to  merge  the  two  in  one,  and-  speak  directly  and 


314  Animal  Life  and  Intelligence. 

simply  of  the  object.  The  object  is  a  thing  I  construct. 
That  it  is  real  may  be  proved  by  submitting  it  to  the  test 
of  all  the  senses  that  I  have. 

And  what  do  I  mean  by  "  real "  ?  I  mean  that  what  it  is 
for  me  it  is  also  for  you  and  any  other  normally  constituted 
human  being.  This  is,  in  truth,  the  only  common-sense 
criterion  of  objective  reality.  Some  people  are  colour-blind, 
and  tell  us  that  a  rose  is  not  red,  but  green.  We  reply 
that  it  is  really  red,  but  that,  through  a  defect  of  sight, 
they  cannot  distinguish  its  redness.  Here  we  take  the 
normal  human  being  as  a  standard  for  objective  reality. 
For  him  the  rose  is  red.  And  this  is  the  only  practical 
criterion  that  we  have.  This,  however,  does  not  satisfy 
some  people,  who  think  that  the  objects  around  them  have 
the  same  reality,  independent  of  man,  that  they  have  for 
us  human-folk.  Annihilate,  they  say,  every  human  being 
— nay,  all  life — and  the  objects  will  remain  as  they  are, 
and  retain  the  same  reality.  Yes,  the  same  reality ;  which 
means  that  if  just  one  fortunate  fellow  escaped  annihilation, 
he  would  find  them  all  just  as  they  were.  And  this  nobody 
doubts.  Nevertheless,  it  is  (to  me,  at  least)  inconceivable 
that  things  independently  of  us  are  what  they  appear  to 
us.  Think  of  what  we  learnt  about  the  sensations.  They 
all  arose  in  stimulations  of  the  end-organs  of  special  sense. 
Thence  the  explosive  waves  of  change  passed  inwards  to 
the  brain,  and  somewhere  therein  gave  rise  to  mental  pro- 
ducts. These  mental  products,  the  accompaniments  of 
nerve-changes,  can  in  no  sense  be  like  the  outside  some- 
thing which  gave  rise  to  them.  They  are  symbols  of  that 
outside  something.  And  it  is  these  symbols  that  we  build 
up  into  objects.  Hence  I  said  that  it  is  not  only  more 
satisfactory  and  convenient,  but  more  correct,  to  speak 
directly  of  the  object  as  constructed,  and  not  our  idea  of 
the  object.  The  mental  product  is  the  object  for  us,  not 
only  for  me,  but  for  you  and  all  normal  human  beings, 
since  the  object  is  the  same  for  all  of  us.  And  hence,  also, 
I  said  that  the  analogy  of  gateways,  through  which  pictures 
of  objects  gain  access  to  the  mind,  was  false  and  misleading, 


Mental  Processes  in  Man.  315 

and  that  a  truer  analogy  is  that  something  stands  without 
and  knocks  at  the  doorway  of  sense,  and  that  from  the 
nature  of  the  knocks  we  learn  somewhat  concerning  that 
which  knocks.  The  person  inside  can  never  open  the  door 
to  see  what  manner  of  thing  it  is  which  knocks.  But  he 
can  build  up  a  most  cunning  symbolism  of  knocks  which 
Bhall  suffice  for  all  practical  purposes.  In  other  words, 
the  object-world,  symbolic  though  it  is,  which  you  and  I 
and  the  rest  of  us  construct  at  the  bidding  of  something 
without  us  (the  existence  of  which  I  assume),  is  amply 
sufficient  for  all  our  practical  needs,  and  constitutes  the 
only  practical  reality  for  human-folk. 

I  am  well  aware  that  there  are  many  people  who 
cannot  bring  themselves  to  believe  in,  or  even  to  listen 
without  impatience  to,  the  view  that  the  world  we  see 
around  us  is  a  world  of  phenomena.  It  is  absurd,  they 
say,  to  tell  us  that  yonder  tulip,'as  an  object,  is  in  any 
sense  dependent  on  our  perception  of  it.  There  it  is,  and 
there  it  would  have  been  had  man  never  been  created. 
Can  one  conceive  that  the  new  species,  of  fossil,  which  was 
only  yesterday  disentombed  from  the  strata  in  which  it  has 
lain  buried  for  long  ages,  is  dependent  on  man's  observa- 
tion for  its  qualities  as  an  object?  To  say  that  it  was 
"constructed"  by  the  lucky  geologist  who  was  fortunate 
enough  first  to  set  eyes  on  it  is  sheer  nonsense.  Its  shelly 
substance  protected  a  bivalve  mollusc  millions  of  years 
before  man  appeared  upon  the  earth.  When  we  see  the 
orange  in  the  fruiterer's  shop,  the  sight  of  it  merely 
reminds  us  of  its  other  qualities — its  taste,  its  smell,  its 
weight,  and  the  rest,  which  are  essentially  its  own,  and  no 
endowments  of  ours — nowise  bestowed  upon  it  by  us. 

I  have  no  hope  of  convincing,  and  not  much  desire  to 
convince,  one  who  thus  objects.  I  would  merely  ask  him 
how  and  when  he  stepped  outside  his  own  consciousness  to 
ascertain  that  these  things  are  so.  Does  he  believe  that 
consciousness  is  an  accompaniment  of  certain  nervous  pro- 
cesses in  the  grey  cortex  of  the  brain  '?  If  so,  let  him  tell 
us  how  these  conscious  accompaniments  resemble  (not 


316  Animal  Life  and  Intelligence. 

merely  symbolize,  but  resemble)  tulips  and  oranges  and 
fossil  molluscs.  If  not,  let  him  propound  his  new  theory 
of  consciousness. 

Let  it  not  be  supposed  that  I  am  denying  the  existence, 
and  the  richly  diversified  existence,  of  the  external  world. 
We  are  fully  justified,  I  think,  in  believing  that,  correspond- 
ing to  the  diversity  of  mental  symbolism,  there  is  a  rich 
diversity  of  external  existence.  But  its  nature  I  hold  that 
we  can  never  know.  The  objects  that  we  see  are  the  joint 
products  of  two  factors — the  external  existence  and  the 
percipient  mind.  We  cannot  eliminate  the  latter  factor 
so  as  to  see  what  the  external  factor  is  like  without  it. 
Those  who,  like  Professor  Mivart,*  say  that  we  can 
eliminate  the  percipient  factor,  and  that  the  external  world 
without  it  is  just  the  same  as  it  is  with  it,  are  content  to 
reduce  the  human  mind,  in  the  matter  of  perception,  to 
the  level  of  a  piece  of  looking-glass. 

There  are  some  people  who  seek  to  get  behind 
phenomena  by  an  appeal  to  evolution.  It  will  not  do 
nowadays,  they  say,  to  make  the  human  mind  a  starting- 
point  in  these  considerations ;  for  the  human  mind  is  the 
product  of  evolution,  and  throughout  that  evolution  has 
been  step  by  step  moulded  to  the  external  world.  The 
external  world  has,  therefore,  the  prior  existence,  and  to  it 
our  perceptions  have  to  conform.  All  this  is  quite  true ; 
but  it  is  beside  the  point.  Mind  has,  throughout  the 
process  of  evolution,  been  moulded  to  the  external  world ; 
our  perceptions  do  conform  to  outside  existences.  But 
they  conform,  not  in  exact  resemblance,  but  in  mental 
symbolism.  They  do  not  copy,  but  they  correspond  to, 
external  existences.  It  is  just  because,  throughout  the 
long  ages  of  evolution,  mind  has  lived  and  worked  in  this 

*  "  Let  the  perception  be  considered  to  be  made  up  of  x  +  y ;  x  being 
the  ego,  or  self,  and  y  the  object.  The  mind  has  the  power  of  supplying  ita 
own  —  z,  and  so  we  get  (through  the  imagination  of  the  mind  and  the  object) 
x  +y  —  x,  or  y  pure  and  simple  "  (Mivart,  "  On  Truth,"  p.  135).  Mr.  Mivart 
devotes  a  whole  section  of  this  work  to  the  defence  of  ordinary  common-sense 
realism.  The  above  assertion  seems  to  contain  the  essence  of  his  teaching  in 
the  matter. 


Mental  Processes  in  Man.  3 1 7 

symbolic  world  that  common  sense  is  unable  to  shake  off 
the  conviction  that  this  is  the  only  possible  world,  and 
exists  as  such  independently  of  mental  processes.  The 
world  of  phenomena  is  the  world  in  which  we,  as  conscious 
beings,  live  and  move.  No  one  denies  it.  But  it  is  none 
the  less  a  symbolic  world;  none  the  less  a  world  which 
mind  has  constructed  in  the  sense  that  it  is  an  inalienable 
factor  in  its  being. 

Each  of  us,  when  we  perceive  an  object,  repeats  and 
summarizes  the  constructive  process  which  it  has  been  the 
end  of  mental  evolution  to  compass.  Hence  it  is  that,  at 
the  bidding  of  a  simple  impression,  percepts  or  constructs 
take  origin  and  shape  in  the  mind.  In  taking  possession 
of  this  faculty  in  the  early  years  of  life,  we  are  entering 
upon  a  rich  ancestral  heritage.  But  if  what  I  have  been 
urging  has  truth,  what  we  call  objects  are  human  con- 
structs, and  cannot  by  any  manipulation  be  converted  into 
anything  else. 

I  will  now  take  another  and  more  complex  case  of 
construction,  which  will  bring  out  some  other  facts  about 
what  I  have  termed  "  constructs."  I  hear  in  the  street  a 
piercing  howl,  which  suggests  a  dog  in  pain.  Eising  from 
my  seat  and  going  to  the  window,  I  see  a  white  terrier 
with  a  black  patch  over  the  left  eye  limping  down  the  road 
on  three  legs.  Now,  what  was  the  nature  of  the  construct 
framed  at  the  bidding  of  the  piercing  howl  ?  A  dog  in 
pain.  But  what  dog  ?  The  nature  of  the  howl  suggested 
a  small  dog ;  but  there  was  nothing  further  to  particularize 
him.  The  construct  was,  therefore,  exceedingly  vague  and 
ill  denned,  and  was  not  rendered  definite  and  particular 
till  I  went  to  the  window,  and  saw  that  it  was  a  white 
terrier  with  a  black  patch  over  the  eye.  The  howl,  more- 
over, suggested  certain  activities  of  the  dog.  The  construct 
was  not  merely  a  passive,  inanimate  object,  like  the  orange, 
but  an  object  capable  of  performing,  and  actually  perform- 
ing, certain  actions.  Here,  again,  we  can  only  say  that  it 
is  through  experience  that  special  activities  are  associated 
with  certain  objects.  Just  as  the  construct  orange  is 


318  Animal  Life  and  Intelligence. 

capable  of  exciting  sensations  of  taste,  so  the  construct  dog 
is  capable  of  doing  certain  things  and  performing  certain 
actions,  that  is,  of  affecting  us  in  certain  further  ways. 

But,  further,  the  howl  suggested  a  dog  in  pain.  No 
amount  of  sensations  entering  into  any  manner  of  relations 
could  give  me  that  element  of  the  construct.  I  can  neither 
see,  touch,  taste,  smell,  nor  hear  pain  in  another  being. 
Pain  is  entirely  subjective  and  known  only  to  the  sufferer. 
But  I  have  been  a  sufferer.  I  have  experienced  pain  and 
pleasure.  And  just  as  my  experiences,  individual  and 
ancestral,  lead  me  to  project  into  inanimate  objects  certain 
qualities,  the  products  of  my  sensations,  so  do  my  ex- 
periences, individual  and  ancestral,  lead  me  to  project  into 
certain  animals  feelings  analogous  to  those  I  have  myself 
experienced.  This  is  sometimes  described  as  an  inference. 
But  if  we  call  this  an  inference,  then  we  must,  I  think,  call 
the  taste,  smell,  and  feel  of  the  orange  I  see  before  me 
inferences.  In  both  cases  the  inference,  if  we  so  call  it, 
enters  at  once  into  the  immediate  construct. 

And  when  I  went  to  the  window  and  saw  the  dog  limp- 
ing down  the  street,  I  saw  also  a  small  boy,  with  arm 
drawn  back,  in  the  act  of  throwing  a  stone.  In  other 
words,  I  saw  the  objects  in  the  scene  before  me  standing  in 
certain  relations  to  each  other.  I  concluded  that  the  boy 
had  thrown  a  stone  at  the  dog  and  was  about  to  throw 
another.  In  other  words,  I  saw  the  scene  before  me  as 
part  of  a  sequence  of  events. 

One  more  example  I  will  give  to  bring  out  another  and 
important  feature  in  the  mental  process.  Strolling  before 
breakfast  in  early  spring  in  my  friend's  garden,  there  is 
borne  to  me  on  the  morning  air  a  whiff  of  violet  fragrance. 
Not  only  does  this  lead  me  to  construct  violets,  but  it 
reminds  me  of  a  scene  in  my  childhood  with  which  the 
scent  of  these  flowers  was  closely  associated.  Not  only  is 
the  object  constructed,  but  a  scene  with  which  their  fragrant 
odour  has  been  associated  is  reconstructed  in  memory.  The 
violets  are  immediate  constructs  or  presentations  of  sense  ; 
the  remembered  scene  is  a  reconstruct  or  representation  in 


Mental  Processes  in  Man.  319 

memory.  So,  too,  when  I  heard  a  piercing  howl  in  the 
street,  the  dog  I  constructed  was  a  vague  presentation  of 
sense ;  but  the  street  in  which  I  instinctively  placed  him 
was  a  reconstruct  or  representation  in  memory.  The 
difference  between  a  construct  or  presentation  of  sense,  and 
a  reconstruct  or  representation  in  memory,  is  that  the 
former  is  directly  suggested  through  the  immediate  action 
of  some  quality  or  activity  of  the  object,  while  the  latter  is 
indirectly  suggested  through  some  intermediate  agency. 

Before  proceeding  further,  let  us  review  the  conclusions 
we  have  thus  far  reached.  Through  the  action  of  certain 
surroundings  on  our  sensitive  organization,  we  receive 
certain  impressions,  and  among  these  impressions  and 
others  revived  in  memory  we  recognize  certain  similarities 
or  differences  in  quality,  in  intensity,  in  order  of  sequence, 
and  in  source  of  origin.  The  sensations  which  thus 
originate  are  mental  facts  in  no  sense  resembling  their 
causes,  but  representing  them  in  mental  symbolism.  The 
consciousness  of  similarity  or  difference  is  no  part  of  the 
impression,  but  a  further  mental  fact  arising  out  of 
the  impression,  and  with  it  giving  origin  to  sensation.  It 
deals  with  the  relation  of  impressions  among  each  other 
and  to  the  recipient.  It  involves  recognition  and  dis- 
crimination. Its  basis  is  laid  in  memory.  The  sensations 
are  instantly  localized,  referred  to  objects,  and  projected 
outwards,  mainly  through  the  instrumentality  of  the 
muscular  sense.  The  mental  symbolism  is  thus  built  into 
the  objects  around  us,  and  constructs  are  formed.  But 
into  the  tissue  of  these  constructs  are  woven,  not  only  the 
sensations  immediately  received,  but  much  that  is  only 
suggested  through  association  as  the  outcome  of  past 
experience,  individual  and  ancestral.  The  constructs  and 
their  associated  reconstructs  are  thus  endowed  with 
qualities  which  have  practical  reality,  since  they  are  not 
for  me  only,  but  for  you  and  for  mankind.  They  are, 
therefore,  in  a  sense  independent  of  me,  but  nowise 
independent  of  man.* 

*  If  it  be  said  that  the  object  does  exist  independently  of  man,  though  not 


320  Animal  Life  and  Intelligence. 

Some  of  the  constructs  are  endowed  with  activities, 
and  some  with  feelings  akin  to  our  own.  Finally,  in  the 
field  of  vision  which  we  construct  or  reconstruct,  the  objects 
are  seen  to  stand  in  relationship  to  each  other,  and  the 
scene  as  a  whole  is  perceived  to  be  part  of  an  orderly 
sequence  of  events. 

We  have  already  got  a  long  way  beyond  the  impressions 
with  which  we  started ;  and  yet,  if  I  may  trust  my  own 
experience,  such  construction  as  I  have  described  is  direct 
and  immediate.  A  child  of  four  or  five  would  not  only 
construct  as  much,  but  might  not  improbably  go  a  long 
way  further,  and  say,  "  Naughty  boy  to  throw  a  stone  at 
poor  doggie  !  "  It  is,  I  say,  direct  and  immediate,  and  it 
implies  a  wonderful  amount  of  mental  activity.  Some 
people  seem  to  imagine  that  in  the  simpler  forms  of  per- 
ception, as  when  I  see  an  orange  on  the  table,  the  mind  is 
as  passive  as  the  sensitive  plate  in  a  photographer's  camera. 
This  surely  is  not  so.  It  is  a  false  and  shallow  psychology 
which  teaches  it.  Just  as  a  light  pin-prick  may  set  agoing 
complex  physical  activities  in  the  frog,  so  may  compara- 
tively simple  visual  sensations  give  rise  to  complex  mental 
activities  in  construction  and  reconstruction.  It  is  to 
emphasize  this  mental  activity  that  I  have  persistently 
used  the  terms  "construct"  and  "construction."  And  I 
wish  to  emphasize  it  still  further  by  saying  that  without 
the  active  and  constructive  mind  no  such  process  of  con- 
struction or  reconstruction  is  possible  or  (I  speak  for 
myself)  conceivable.  We  might  just  as  well  suppose  that 
the  frog  could  leap  away  on  stimulation  of  a  pin-prick  in 
the  absence  of  its  complex  bodily  organization,  as  that 
sensation  could  give  rise  to  construction  and  reconstruc- 
tion in  the  absence  of  a  highly  organized  mind. 

We  have  seen  that  when  a  howl  suggested  the  construct 
dog,  that  construct  was  vague  and  undefined ;  but  when  I 

in  the  phenomenal  guise  tinder  which  we  know  it,  I  would  reply — Not  so  ; 
for  it  is  to  the  existence  under  this  phenomenal  guise  that  we  apply  the  word 
"  object."  In  philosophical  language,  the  existence,  stripped  of  its  pheno- 
menal aspect,  is  called  the  Ding  an  8ich.  Its  essential  character  is  ita  inde- 
pendence of  man ;  and  hence  its  unknowability. 


Mental  Processes  in  Man.  321 

went  to  the  window  and  saw  the  terrier,  the  construct 
became  particularized  and  denned.  This  seems  to  me  the 
normal  order  of  development :  first  the  vague,  general, 
and  indefinite;  then  the  particular,  special,  and  defined. 
That  which  is  immediately  suggested  at  the  bidding  of 
sensations  received  is  always  more  or  less  general ;  it  only 
becomes  specialized  on  further  examination  physical  or 
mental — first  a  dog  or  an  orange ;  then  this  dog  or  this 
orange.  The  more  unfamiliar  the  object,  the  more  vague 
and  indefinite  the  construct.  The  more  familiar  the  object, 
and  the  further  our  examination  of  it  is  carried,  the  more 
particular  and  defined  the  construct.  I  would,  therefore, 
mark  two  stages  in  the  process  of  construction :  first,  the 
formation  of  constructs  by  immediate  association,  more  or 
less  vague,  indefinite,  and  ill  defined ;  and,  secondly,  the 
definition  of  constructs  by  examination,  by  which  they  are 
rendered  more  definite,  particular,  and  special,  and  supple- 
mented by  intelligent  inferences. 

I  need  not  stay  here  to  point  out  the  immense  im- 
portance vof  this  process  of  defining  and  particularizing 
constructs,  or  the  length  to  which  it  may  be  carried ;  nor 
need  I  pause  to  indicate  how,  through  memory  and 
association,  representative  or  reconstructive  elements  crowd 
in  to  link  or  weave  the  constructs  into  more  or  less  vivid 
and  brilliant  scenes.  But  I  have  next  to  notice  that  out 
of  this  intelligent  examination  arises  a  new,  distinct 
mental  process,  the  analysis  of  constructs. 

This  process  involves  the  paying  of  special  attention  to 
certain  qualities  of  objects,  to  the  intentional  exclusion  of 
other  qualities.  "When  I  cease  to  examine  an  orange  as  a 
construct,  and  pay  attention  to  its  colour  or  its  taste  to  the 
exclusion  of  other  properties,  with  the  purpose  of  comparing 
this  colour  or  taste  with  other  colours  and  tastes,  I  am 
making  a  step  in  analysis.  So,  too,  when  I  consider  the 
form  of  an  orange  for  the  purpose  of  comparing  it  with  the 
form  of  the  earth,  I  am  making  a  step  in  analysis.  And, 
again,  when  I  consider  the  howl  of  the  dog  with  the  object 
of  comparing  it  with  other  sounds,  I  am  making  a  step  in 

Y 


322  Animal  Life  and  Intelligence. 

analysis.  We  may  call  the  process  by  which  we  select  a 
certain  quality,  and  consider  it  by  itself  to  the  neglect  of 
other  qualities,  isolation,  and  the  products  of  the  process 
we  may  term  isolates* 

This  process  could  not  be  initiated  till  a  large  body  of 
constructive  and  reconstructive  experience  had  been  gained. 
But  once  initiated,  there  is  no  end  to  the  process.  We 
pick  to  pieces  all  the  phenomena  of  nature,  all  the  qualities 
and  relationships  of  objects,  the  activities  and  functions  of 
animals,  the  mental  phenomena  of  which  we  are  conscious 
in  ourselves.  We  isolate  the  qualities,  relationships,  feel- 
ings ;  and  we  name  the  isolates  we  obtain.  Hence  arises 
all  our  science,  all  our  higher  thought.  In  the  terms 
which  we  apply  to  our  isolates  consists  the  richness  of  our 
language. 

We  name  the  isolates ;  that  is,  we  apply  to  each  an 
arbitrary  symbol  to  stand  for  the  isolated  quality  or  rela- 
tion. All  words  (except  the  obviously  onomatopoetic,  such 
as  "  bow-wow,"  "  cuckoo,"  etc.)  are  arbitrary  symbols 
associated  with  objects,  or  qualities,  or  relations,  or  other 
phenomena.  And  abstract  names  of  isolates  are,  so  to 
speak,  the  pegs  on  which  we  hang  the  qualities  we  have 
separated  by  analysis  and  isolation,  while  class-names  are 
pegs  upon  which  we  can  hang  a  group  of  similars  reached 
by  the  process  of  isolation ;  for  all  classing  and  grouping 
of  objects,  or  qualities,  or  relations  involves,  so  far  as  the 
process  is  a  conscious  one,  the  principle  of  analysis.  In 
classing  objects,  we  group  them  in  reference  to  certain 
characters  which  they  have  in  common,  disregarding 
certain  other  characters  in  which  they  differ.  We  group 
together,  for  example,  sights,  or  sounds,  or  smells,  and 
distinguish  them  from  each  other  and  from  tastes  and 
touches.  And  then  we  go  further,  and  class  all  these 
together  as  sensations  having  certain  characteristics  in 
common  whereby  they  are  distinguished  from  perceptions 
of  relation  arid  so  forth. 

*  I  avoid,  for  the  present,  the  use  of  the  terms  "  abstraction  "  and  "  abstract 
idea  "  because  they  are  employed  in  different  senses  by  different  authors. 


Mental  Processes  in  Man.  323 

Perhaps  it  may  be  objected  that  clasBification  comes 
much  earlier  in  the  mental  process  than  I  am  now  putting 
it.  It  may  be  said  that  the  recognition  of  a  sensation  as 
a  touch,  or  a  smell,  or  a  sound  involves  a  classification  of 
sensations  in  these  categories,  and  that  the  simple  percep- 
tion of  an  orange  involves  the  placing  of  the  object  in 
this  class  of  bodies.  And,  undoubtedly,  we  have  here  the 
germs  of  the  process.  Sensation  and  perception  give  us 
the  materials  for  classification ;  the  perception  of  similarity 
and  difference  gives  us  the  sine  qua  non  of  the  process. 
Nevertheless,  although  there  may  be  an  earlier  unconscious 
grouping  of  phenomena,  it  is  only  when  the  mind  is 
specially  directed  to  these  materials,  with  the  object  of 
grouping  them  according  to  their  similarities,  that  we  can 
speak  of  classification  proper — conscious  and  intentional 
classification,  as  opposed  to  unconscious  grouping.  And 
this  involves  the  intentional  selection  of  the  points  of 
similarity,  and  discarding  or  neglecting  the  points  of 
difference.  It  involves  the  process  of  analysis  or  isolation. 
There  is  a  vast  difference  between  the  perceptual  recogni- 
tion of  objects  as  similar,  and  conceptual  classification 
on  grounds  of  similarity.  Just  as  the  recognition  of  a 
sensation  as  now  and  not  then,  or  here  and  not  there,  or 
as  due  to  something  outside  us,  gives  us  the  germs  from 
which,  on  ultimate  analysis,  our  ideas  of  time,  space,  and 
causation  are  reached;  so  does  the  recognition  of  these 
sensations  as  of  this  kind  and  not  that  give  us  the  germ 
from  which,  on  analysis,  the  process  of  classification  may 
arise.  True,  conscious,  scientific  classification  is  late  in 
development. 

And  here  let  us  notice  that  the  conclusions  we  have 
reached  in  this  chapter  are  the  outcome  of  analysis  and 
classification.  The  sensations  with  which  we  started  are 
isolates.  In  considering  their  quality,  intensity,  sequence, 
we  were  isolating  and  classifying  these  special  modes  of 
their  existence.  Localization  and  outward  projection  in- 
volved isolation.  We  simply  see  the  orange  before  us.  To 
understand  and  explain  how  we  come  to  see  it  as  we  do 


324  Animal  Life  and  Intelligence. 

see  it  involves  a  somewhat  subtle  analysis.  We  perceive 
it  to  be  yellow,  round,  resistant ;  and  then,  isolating  these 
qualities,  we  reach  conceptions  of  yellowness,  roundness, 
and  resistance,  quite  apart  from  oranges.  Throughout  our 
description  the  terms  we  used  were  very  largely  terms 
denoting  classified  isolates. 

Lastly,  having  enormously  increased  our  knowledge  by 
this  process  of  isolation,  we  proceed  to  build  in  the  know- 
ledge thus  gained  to  the  structure  of  our  constructs.  This 
is  the  third  and  last  stage  in  construction.  The  first  stage 
is  the  formation  of  indefinite  constructs  by  immediate 
association ;  the  second  is  the  definition  of  constructs  by 
examination  ;  and  the  third  is  the  completion  of  constructs 
by  synthesis. 

And  the  further  this  process  of  analysis  and  isolation 
is  carried,  the  more  we  are,  so  to  speak,  floated  off  from 
the  immediate  objects  of  sense  into  the  higher  regions  of 
abstract  thought.  Furthermore,  by  recombining  our  iso- 
lates in  new  modes  and  under  new  relations,  we  reach  the 
splendid  results  of  constructive  imagination. 

In  the  brief  description  which  I  have  now  given  of  our 
mental  processes,  I  have  for  the  most  part  avoided  certain 
terms  which  are  current  in  the  science  of  psychology.  It 
will  be  well  here  to  say  a  few  words  concerning  these  words 
and  their  use.  The  process  of  sensation  is  sometimes 
defined  as  the  mere  reception  of  a  sense-stimulus.  But 
it  is  more  convenient,  and  more  in  accordance  with  common 
usage,  to  call  the  simple  result  of  a  stimulus  an  impres- 
sion, and  to  apply  the  term  "sensation  "  to  the  discrimina- 
tion and  recognition  of  the  impressions  as  of  such  and  such 
a  quality.  Sensation,  then,  is  the  reception  and  discrimina- 
tion of  impressions  which  result  from  certain  modes  of 
influence  (stimuli)  brought  to  bear  on  our  organization. 
Viewed  in  this  way,  therefore,  even  sensation  involves  a 
distinct  reaction  of  the  mind  ;  it  implies  the  first  stage  of 
mental  activity.  But  when  the  sensations  are  given 
objective  significance,  when  they  suggest  the  existence  of 
an  object- world  without  us,  they  enter  the  field  of  percep- 


Mental  Processes  in  Man.  325 

tion.  Here  the  discriminated  sense-impression  is,  to  use 
the  words  of  Mr.  Sully,  "  supplemented  by  an  accompani- 
ment or  escort  of  revived  sensations,  the  whole  aggregate 
of  actual  and  revived  sensations  being  solidified  or  inte- 
grated into  the  form  of  a  percept;  that  is,  an  apparently 
immediate  apprehension  or  cognition  of  an  object  now 
present  in  a  particular  locality  or  region  of  space."* 
Throughout  the  whole  process  of  the  formation  of  con- 
structs by  immediate  association,  and  their  definition  by 
examination,  we  were  dealing  with  perception  and  percepts. 
But  when  we  reach  the  stage  when  particular  qualities 
were  isolated,  then  we  enter  the  field  of  conception.  The 
isolates  are  concepts.  Class-names,  reached  through  pro- 
cesses involving  isolation,  stand  for  concepts.  And  com- 
pleted constructions,  involving  synthesis  of  the  results  of 
analysis,  contain  conceptual  elements.  The  word  "  con- 
cept," however,  is  used  in  different  senses  by  different 
authors.  Mr.  Sully  says,f  for  example,  "  A  concept, 
otherwise  called  a  general  notion,  or  a  general  idea,  is 
the  representation  in  our  minds  answering  to  a  general 
name,  such  as  '  soldier,'  '  man,'  '  animal.'  .  .  .  Thus  the 
concept  '  soldier  '  is  connected  in  my  mind  with  the  repre- 
sentations of  various  individual  soldiers  known  to  me. 
When  I  use  the  word  '  soldier/  .  .  .  what  is  in  my  mind 
is  a  kind  of  composite  image  formed  by  the  fusion  or 
coalescence  of  many  images  of  single  objects,  in  which 
individual  differences  are  blurred,  and  only  the  common 
features  stand  out  distinctly.  .  .  .  This  may  be  called  a 
typical  or  generic  image."  But  Noire,  quoted  by  Professor 
Max  Miiller,}  taking  another  illustration,  says,  "  All  trees 
hitherto  seen  by  me  leave  in  my  imagination  a  mixed 
image,  a  kind  of  ideal  presentation  of  a  tree.  Quite 
different  from  this  is  my  concept,  which  is  never  an  image." 
I  follow  Noire ;  and  I  hold  that  the  image,  in  so  far  as  it 
is  an  image,  whether  simple  or  composite, §  is  a  percept; 

*  "  Outlines  of  Psychology,"  p.  153.  f  Ibid.  p.  339, 

J  "  Science  of  Thought,"  p.  453. 

§  For  compound  or  generic  ideas  "not  consciously  fixed  and  signed   by 


326  Animal  Life  and  Intelligence. 

but  that,  in  so  far  as  there  enter  into  the  idea  of  the 
soldier  or  the  tree  elements  which  have  been  isolated  by 
analysis,  just  in  so  far  does  the  word  "  soldier  "  or  "  tree  " 
stand  for  a  concept.  How  far  a  word  stands  for  a  percept, 
and  how  far  there  enter  conceptual  elements,  depends  to 
a  large  extent  on  the  level  of  intelligence  of  the  hearer. 
The  moment  educated  and  intellectual  folk  begin  to  think 

means  of  an  abstract  name,"  Mr.  Romanes  ("  Mental  Evolution  in  Man,"  p. 
36)  has  suggested  the  term  "  recept."  In  the  photographic  psychology  which 
he  adopts,  the  percept  is  an  individual  and  particular  photograph,  the  recept  a 
generalized  or  composite  photograph.  "  The  word '  recept,' "  he  says,  "  is  seen 
to  be  appropriate  to  the  class  of  ideas  in  question,  because,  in  receiving  such 
ideas,  the  mind  is  passive."  This,  it  will  be  observed,  is  in  opposition  to  the 
teaching  of  this  chapter,  in  which  the  activity  of  the  mind  in  perception  has 
been  insisted  on.  Mr.  Romanes's  recepts  answer  in  part  to  what  I  have 
termed  constructs,  which,  as  we  have  seen,  are,  as  a  rule,  from  the  first  general 
rather  than  particular,  and  in  part  to  concepts  reached  through  analysis.  Mr. 
Romanes,  for  example,  speaks  of  ideas  of  principles  (e.g.  the  principle  of  the 
screw)  and  ideas  of  qualities  (e.g.  good-for-eating  and  not-good-for-eating)  as 
recepts  (p.  60).  On  the  other  hand,  Mr.  Mivart  ("  The  Origin  of  Human 
Reason,"  p.  59 ;  see  also  his  work  "  On  Truth  ")  terms  such  generic  affections 
'•  sensuous  universals."  It  may  be  well  to  append  Mr.  Romanes's  and  Mr. 
Mivart's  tabular  statements. 

Mr.  Romanes. 

(General,  abstract,  or  notional       =     Concepts. 
Complex,  compound,  or  mixed     =     Recepts,  or 

generic  ideas. 

{  Simple,  particular,  or  concrete     =     Memories  of  per- 
cepts. 

Mr.  Mivart. 

-_,  /  General  or  true  universals  =     Concepts. 

IDEAS        \Particularorindividual  =     Percepts. 

Groups  of  actual  experiences  | 


SENSITIVE     COGXI- 


combined  with   sensuous 


.1.,  or  recepts. 


1      Groups  of  simply  juxtaposed^        .     Sense-perceptions, 
actual  experiences  /  or  sencepts. 

In  Mr.  Mivart's  terminology,  the  representations  of  the  lower  group  are 
"mental  images"  or  "  phantasmata."  The  term  "  consciousness  "  is  by  him 
restricted  to  the  higher  region  of  ideas,  the  term  "  consentience  "  being  applied 
to  the  faculty  by  which  cognitive  affections  are  felt,  unified,  and  grouped 
without  consciousness.  There  is  a  difference  in  kind,  according  to  Mr.  Mivart, 
between  "  consentience  "  and  "  consciousness  ;  "  and  the  former  could  therefore 
never  develop  into  the  latter,  nor  the  latter  be  evolved  from  the  former.  For 
this  reason  (because  of  the  philosophy  it  is  intended  to  carry  with  it)  I  shall 
not  employ  the  word  "consentience,"  which  would  otherwise  be  a  useful 
term. 


Mental  Processes  in  Man.  327 

about  their  words,  or  the  objects  for  which  they  stand, 
conceptual  elements  are  sure  to  crowd  in. 

There  is  one  more  feature  of  these  mental  processes  in 
man,  and  that  by  no  means  the  least  important,  that 
remains  for  brief  consideration.  I  began  by  saying  that 
the  primary  end  and  object  of  the  reception  of  the  influences 
of  the  external  world,  or  environment,  is  to  enable  the 
organism  to  answer  to  them  in  activity.  We  saw  that  the 
sight  of  an  orange  suggests,  through  association,  its  taste  ; 
and  that  the  validity  of  the  association  could  be  verified  by 
going  to  the  orange  and  tasting  it.  We  saw,  too,  that 
when  I  heard  a  dog  howl  in  the  street,  and,  going  to  the 
window,  saw  a  small  boy  with  a  stone  in  his  hand,  I  con- 
cluded that  he  was  going  to  throw  it  at  the  dog.  What  I 
wish  now  to  elicit  is  that  out  of  perceptions  through  asso- 
ciation there  arise  certain  expectations,  and  that  the 
activities  of  organisms  are  moulded  in  accordance  with 
these  expectations. 

It  is  clear  that  these  expectations  or  anticipations 
belong  partly  to  the  presentative  or  constructive  order,  and 
partly  to  the  reconstructive  or  representative  order.  They 
are  in  some  cases  directly  suggested  by  the  presentations 
of  sense ;  they  are  also  built  up  out  of  representations 
which  have  become  associated  with  the  constructs  in 
memory  and  through  experience.  But  what  we  have  here 
especially  to  notice  about  them  is  that,  in  the  latter  case, 
they  involve  more  or  less  distinctly  the  element  which  we, 
in  the  language  of  our  developed  thought,  call  causation. 
There  is  a  sequence  of  events,  and  the  perception  of  certain 
of  these  gives  rise,  through  association  and  experience,  to 
an  expectation  of  certain  succeeding  phenomena.  Expecta- 
tions are,  therefore,  the  outcome  of  the  linked  nature  of 
phenomena.  And  when  we  come  eventually  to  think  about 
the  phenomena,  and  how  they  are  linked  together  into  a 
chain  (successional)  or  web  (coexistent),  we  reach  the  con- 
ception of  causation  as  the  connecting  thread.  In  early 
stages  of  the  mental  process,  such  a  conception  does  not 
emerge.  Nevertheless,  the  phenomena  are  perceived  as 


328  Animal  Life  and  Intelligence. 

linked  or  woven.  And  the  mental  process  by  which  we 
pass  from  any  perceived  event  or  existence  to  other  pre- 
ceding, concomitant,  or  subsequent  events  or  existences 
linked  or  woven  with  it  in  the  chain  or  web  of  phenomena, 
we  call  inference*  When,  for  example,  I  find  a  footprint 
in  the  sand,  I  infer  that  a  man  has  passed  that  way ;  and 
when  the  clouds  are  heaped  up  heavy  and  black,  I  infer 
that  a  storm  is  about  to  burst  upon  us. 

Concerning  inference,  of  which  I  shall  have  more  to 
say  in  the  next  chapter,  I  have  now  to  note  that  it  is  of 
two  kinds :  first,  perceptual  inference,  or  inference  from 
direct  experience  ;  secondly,  conceptual  inference,  or  infer- 
ence based  on  experience,  but  reached  through  the  exercise 
of  the  reasoning  faculties.  The  latter  involves  the  process 
of  analysis  or  isolation ;  the  former  does  not.  There  is  a 
marked  difference  between  the  two.  Perceptual  inferences 
are  the  outcome  of  practical  experience,  but  do  not  go 
beyond  euch  practical  experience.  Conceptual  inferences 
are  also  based  on  experience,  but  they  predict  occurrences 
never  before  experienced.  Perceptual  inferences,  again, 
deal  with  matters  practically;  but  conceptual  thought 
explains  them. 

The  expectation  of  a  storm  when  the  thunder-clouds  are 
heavy  is  a  case  of  perceptual  inference.  It  is  the  outcome 
of  a  long-established  association,  and  is  not  reached  by  a 
process  of  reasoning  involving  an  analysis  of  the  pheno- 
mena. But  if,  though  the  sky  is  clear,  a  west  wind  and 
a  rapidly  falling  barometer  lead  me  to  predict  rain,  the 
inference  is  conceptual,  and  gained  by  me  or  for  me  by  a 
process  of  reasoning ;  for  the  barometer  was  the  outcome 
of  the  analysis  of  phenomena.  In  the  mind  of  the  rough 
sailor-lad,  however,  the  fall  of  the  mercury  and  the  suc- 
ceeding storm  may  be  connected  by  mere  perceptual 

*  We  do  not  speak  of  the  filling  in  the  complement  of  a  percept  (the  con- 
struction of  the  object  at  the  bidding  of  a  simple  impression)  as  a  matter  of 
conscious  inference.  I  do  not  consciously  infer  that  yonder  moss-rose  is 
scented.  Scent  is  an  integral  part  of  the  construct.  From  the  appearance  of 
the  rose,  I  may,  however,  infer  that  a  rose-chafer  has  disturbed  its  petals. 
The  complement  of  the  percept,  if  inferred  at  all,  is  unconsciously  inferred. 


Mental  Processes  in  Man.  329 

inference,  the  phenomena  being  simply  associated  together. 
If,  however,  there  is  any  attempt  at  explanation,  correct  or 
incorrect,  there  is  so  far  a  conceptual  element.  In  a  little 
fishing-village  on  our  south  coast,  a  benevolent  lady 
presented  the  fishermen  with  a  Fitzroy  barometer.  I 
happened  shortly  after  to  remark  to  one  of  the  men  that 
the  summer  had  been  unusually  stormy.  "  Yes,  sir,"  he 
said,  "  it  has.  But  then,  you  see,  the  weather  hasn't  no 
chance  against  that  new  glass."  Here  there  was  an 
attempted  explanation  of  the  phenomena.  The  falling 
glass  was  conceived  as  somehow  causing  bad  weather. 

It  is  hard  to  draw  the  line  between  perceptual  and  con- 
ceptual inferences,  or  rather  to  say,  in  this  or  that  case,  to 
which  class  the  inference  belongs,  because  man,  through 
language,  lives  in  a  conceptual  atmosphere.  Moreover, 
the  same  result  may,  in  different  cases,  be  reached  by  per- 
ceptual or  by  conceptual  inference.  A  child  who  had  seen 
a  great  number  of  ascending  balloons  might,  on  seeing  a 
balloon,  expect  it  to  ascend  by  a  perceptual  inference ;  but 
a  man,  knowing  that  the  balloon  was  full  of  a  gas  lighter 
than  air,  might  expect  it  to  ascend  through  the  exercise  of 
conceptual  inference.  And  just  as  in  adult  civilized  life 
our  constructs  have  more  and  more  conceptual  elements 
built  into  them,  so  do  our  inferences  become  more  and 
more  reasoned.  It  is  probable  that  in  an  adult  English- 
man every  inference  has  a  larger  or  smaller  dose  of  the 
conceptual  element. 

With  the  development  of  language  we  state  our  in- 
ferences in  the  form  of  propositions,  and  call  them 
judgments.  "  Every  proposition,"  says  Mr.  Sully,*  "  is 
made  up  of  two  principal  parts :  (1)  the  subject,  or  the 
name  of  that  about  which  something  is  asserted ;  (2)  the 
predicate,  or  the  name  of  that  which  is  asserted.  Thus, 
when  we  affirm,  '  This  knife  is  blunt,'  we  affirm  or 
predicate  the  fact  of  being  blunt  of  a  certain  subject, 
namely,  'this  knife.'  Similarly,  when  we  say,  'Air 
corrodes,'  we  assert  or  predicate  the  power  of  corroding  of 
*  "  Outlines  of  Psychology,"  p.  392. 


330  Animal  Life  and  Intelligence. 

the  subject  '  air.'  "  The  proposition  always  involves  con- 
ceptual elements;  for  the  predicate  of  a  proposition  is 
always  an  abstract  idea  or  general  notion. 

Propositions  so  formed  may  then  become  links  in  a 
chain  of  reasoning.  "  To  reason  is,"  says  Mr.  Sully,*  "to 
pass  from  a  certain  judgment  or  certain  judgments  to  a 
new  one."  And  so  passing  on  from  judgment  to  judgment, 
we  may  ascend  to  the  higher  levels  of  abstract  thought. 
According  to  Mr.  Sully's  definition,  therefore,  we  start  from 
a  judgment  or  judgments  in  the  process  of  reasoning. 
The  formation  of  a  judgment  (conceptual  inference)  is, 
however,  the  first  step  in  a  continuous  process  ;  and  I  pro- 
pose, under  this  term,  "reason,"  f  to  include  this  first  step 
also.  The  formation  of  a  conceptual  inference  I  regard  as 
the  first  stage  of  reason.  Any  mental  process  involving 
conceptual  inference  I  shall  call  rational. 

In  contradistinction  to  this,  I  shall  use  the  term  "  in- 
telligence "  for  the  processes  by  which  perceptual  inferences 
are  reached.  An  intelligent  act  is  an  act  performed  as  the 
outcome  of  merely  perceptual  inference.  A  rational  act  is 
the  outcome  of  an  inference  which  contains  a  conceptual 
element. 

*  "  Outlines  of  Psychology."  p.  414. 

t  Mr.  Romanes  adopts  a  different  use  of  the  terms  "  reason"  and  "  rational," 
to  which  allusion  will  be  made  in  the  nest  chapter. 


CHAPTEE  IX. 

MENTAL  PROCESSES  IN  ANIMALS  :    THEIR  POWERS   OF  PERCEPTION 
AND    INTELLIGENCE. 

Two  things  I  have  been  especially  anxious  to  bring  out 
prominently  in  the  foregoing  chapter :  first,  that  the 
world  we  see  around  us  is  a  joint  product  of  two  factors 
— the  outward  existence,  on  the  one  hand,  and  our  active 
mind  on  the  other;  and  secondly,  that  our  mental  pro- 
cesses and  products  fall  under  two  categories — on  the  one 
hand,  perception,  giving  rise  to  percepts,  perceptual 
inferences,  and  intelligence,  and  on  the  other,  conception 
(involving  the  analysis  of  phenomena),  giving  rise  to  con- 
cepts, conceptual  inferences,  and  reason. 

Now,  I  am  anxious  that  the  former — to  take  that  first — 
should  be  laid  hold  of  and  really  grasped  as  an  indubitable 
fact.  It  is  implied  in  the  word  "  phenomena,"  that  is  to  say, 
appearances.  We  can  only  know  the  world  as  it  appears 
to  us ;  and  the  world  is  for  us  what  it  appears.  There  is 
nothing  here  in  conflict  with  common  sense ;  the  practical 
reality  of  phenomena  is  altered  no  whit.  Suppose  philosophy 
tries  to  get  behind  phenomena,  so  as  to  get  a  peep  at  the 
world  beyond.  Suppose  Carlyle  tells  us  that  "  All  visible 
things  are  emblems ;  what  thou  seest  is  not  there  on  its 
own  account ;  strictly  taken,  is  not  there  [as  such]  at  all ; 
matter  exists  only  spiritually,  and  to  represent  some  idea 
and  body  it  forth."  Has  he  altered  the  reality  of  the 
phenomena  themselves  ?  Not  in  the  smallest  degree. 
Suppose  the  materialist  gives  us  his  analysis  of  pheno- 
mena. Are  not  the  phenomena  he  analyzes  still  the  same, 
still  equally  real  ?  No  matter  how  far  he  analyzes  pheno- 


Animal  Life  and  Intelligence. 


mena,  behind  phenomena  he  cannot  get.  The  materialist 
resolves  all  phenomena  into  matter  in  motion  or  into 
energy,  and  says  that  these  are  the  only  real  existences. 
But  they  are  no  more  real  (they  are  a  good  deal  less  real 
to  most  of  us)  than  the  phenomena  with  which  he  started. 
How  can  the  results  of  analysis  be  more  real  than  that 
which  is  analyzed  ?  Moreover,  the  matter  and  energy  are 
still  phenomena,  and  involve,  as  such,  the  percipient  mind. 
Do  what  you  will,  you  cannot  get  rid  of  the  mental  factor 
in  phenomena. 

It  is  possible  that  my  use  of  the  word  "  construct,"  my 
saying  that  the  object  is  a  thing  which  each  of  us  constructs 
at  the  suggestion  of  certain  sense-stimuli,  may  lead  some 
to  suppose  that  the  process  is  in  some  sense  an  arbitrary 
one.  This,  however,  would  be  a  misconception.  The 
process  under  normal  conditions  is  just  as  inevitable  as  is, 
under  ^normal  conditions,  the  fall  of  a  stone  to  the  ground. 
The  law  of  construction  for  human-folk  is  as  much  a  law 
of  nature  as  the  law  of  gravitation.  Both  laws  are  con- 
densed statements  of  the  facts  of  the  case.  There  is 
nothing  arbitrary,  lawless,  or  unnatural  in  the  one  or  the 
other ;  tho  phrase  merely  emphasizes  the  essential  presence 
of  the  mental  factor. 

If  this  principle  be  once  thoroughly  grasped,  it  will  be 
seen  how  shallow  and  misleading  is  the  view  that  the 
world  is  just  reflected  in  consciousness  unchanged  as  in  a 
mirror,  or  faithfully  photographed  as  on  a  sensitive  plate. 
This  is  to  reduce  the  human  mind,  which  is  surely  no  whit 
less  complex  than  the  human  body,  to  the  condition  of  a 
mere  passive  recipient  instead  of  a  vital  and  active  agent 
in  the  construction  of  man's  world. 

The  next  point  we  have  to  consider  is  why  we  believe, 
as  you  and  I  practically  do  believe,  that  the  world  of 
phenomena  exists  as  such,  not  merely  for  you  and  for  me, 
but  for  man.  Is  it  not  because  we  believe  in  the  practical 
unity  of  mankind  ?  Is  it  not  because  we  believe  that, 
greatly  as  the  conceptual  and  intellectual  superstructure 
may  differ  in  different  individuals,  the  perceptual  basis 


Mental  Processes  in  Animals.  333 

and  foundation  are  practically  identical  ?  The  senses  and 
sense-organs  give,  in  all  normal  individuals,  sense-data, 
which  differ  only  within  comparatively  narrow  limits ;  and 
though  the  intellectual  and  moral  world  of  the  Bushman 
and  the  North  Australian  may  differ  profoundly  from  those 
of  Shakespeare  and  Pascal,  the  perceptual  world  is,  we 
have  every  reason  to  suppose,  within  these  narrow  limits, 
the  same.  This  we  may  fairly  believe ;  but  even  so  there 
must  be,  nay,  we  know  that  there  are,  very  great  differences 
in  the  interpretation  of  the  perceptual  world.  The  indi- 
vidual cannot  divest  himself  of  the  intellectual  and  con- 
ceptual part  of  his  nature.  We,  for  whom  phenomena  are 
more  or  less  conditioned  by  science,  find  it  difficult  to 
think  ourselves  into  the  position  of  the  savage,  whose 
perceptual  world  is  conditioned  by  crude  superstition. 
The  elements  of  his  perceptual  world  are  the  same  as 
ours,  but  the  light  of  knowledge  in  which  we  view  them  is, 
for  him,  very  dim.  When  we  try  to  realize  his  world  we 
find  it  exceedingly  difficult. 

And  when  we  come  to  the  lower  animals — even  those 
nearest  us  in  the  scale  of  life — the  difficulties  are 
enormously  increased.  The  sense-data  are  probably  much 
the  same,  but  they  are  combined  in  different  proportions. 
Olfactory  sensation  must,  one  would  suppose,  be  built  into 
the  constructs  of  the  dog  and  the  deer  to  an  extent  which 
we  cannot  at  all  realize.  And  then,  as  Mr.  P.  G.  Hamerton 
has  well  said,  we  have  to  take  into  account  the  immensity 
of  the  ignorance  of  animals.  That  ignorance,  in  combina- 
tion with  perfect  perceptual  clearness  (ignorance  and 
mental  clearness  are  quite  compatible)  and  with  incon- 
ceivably strong  instincts,  produces  a  creature  whose  mental 
states  we  can  never  accurately  understand. 

I  am  tempted  here  to  give  the  instance  Mr.  Hamerton 
quotes  *  in  illustration  of  the  ignorance  of  animals. 

"  The  following  account  of  the  behaviour  of  a  cow,"  he 
says,  "  gives  a  glimpse  of  the  real  nature  of  the  animal. 
These  long-tailed  cows,  say  Messrs.  Hue  and  Gabet,  are  so 

*  "  Chapters  on  Animals,"  p.  9. 


334  Animal  Life  and  Intelligence. 

restive  and  difficult  to  milk,  that  to  keep  them  at  all  quiet 
the  herdsman  has  to  give  them  a  calf  to  lick  meanwhile. 
But  for  this  device,  not  a  single  drop  of  milk  can  be  obtained 
from  them.  One  day  a  Llama  herdsman,  who  lived  in  the 
same  house  as  ourselves,  came  with  a  long  dismal  face  to 
announce  that  his  cow  had  calved  during  the  night,  and 
that,  unfortunately,  the  calf  was  dying.  It  died  in  the 
course  of  the  day.  The  Llama  forthwith  skinned  the  poor 
beast  and  stuffed  it  with  hay.  This  proceeding  surprised 
us  at  first,  for  the  Llama  had  by  no  means  the  air  of  a  man 
likely  to  give  himself  the  luxury  of  a  cabinet  of  natural 
history.  When  the  operation  was  completed,  we  found 
that  the  hay-calf  had  neither  feet  nor  head ;  whereupon  it 
occurred  to  us  that,  after  all,  it  was  perhaps  a  pillow  that 
the  Llama  contemplated.  We  were  in  error,  but  the  error 
was  not  dissipated  till  the  next  morning,  when  our  herds- 
man went  to  milk  his  cow.  Seeing  him  issue  forth,  the 
pail  in  one  hand  and  the  hay-calf  under  the  other  arm,  the 
fancy  occurred  to  us  to  follow  him.  His  first  proceeding 
was  to  put  the  hay-calf  down  before  the  cow.  He  then 
turned  to  milk  the  cow  herself.  The  mamma  at  first 
opened  enormous  eyes  at  her  beloved  infant ;  by  degrees 
she  stooped  her  head  towards  it,  then  smelt  at  it,  sneezed 
three  or  four  times,  and  at  last  proceeded  to  lick  it  with 
the  most  delightful  tenderness.  This  spectacle  grated 
against  our  sensibilities ;  it  seemed  to  us  that  he  who  first 
invented  this  parody  upon  one  of  the  most  touching 
incidents  in  nature  must  have  been  a  man  without  a  heart. 
A  somewhat  burlesque  circumstance  occurred  one  day  to 
modify  the  indignation  with  which  this  treachery  inspired 
us.  By  dint  of  caressing  and  licking  her  little  calf,  the 
tender  parent  one  fine  morning  unripped  it.  The  hay 
issued  from  within,  and  the  cow,  manifesting  not  the 
slightest  surprise  nor  agitation,  proceeded  tranquilly  to 
devour  the  unexpected  provender." 

Are  we  surprised  at  the  want  of  surprise  on  the  part 
of  the  cow  ?  Why  should  we  be  ?  What  knows  she  of 
anatomy  or  of  physiology  ?  If  she  could  think  at  all  about 


Mental  Processes  in  Animals.  335 

the  matter,  she  would,  no  doubt,  have  expected  her  calf  to 
be  composed  of  condensed  milk.  But  failing  that,  why 
not  hay  ?  She  had  presumably  some  little  experience  of 
putting  hay  inside.  Why  noifind  hay  inside  ;  and,  finding 
hay,  why  not  enjoy  the  good  provender  thus  provided  ? 
But  clearly  we  must  not  expect  the  brutes  to  possess  know- 
ledge to  which  they  cannot  attain  about  matters  which  in 
no  wise  concern  their  daily  life. 

"In  our  estimates  of  the  characters  of  animals,"  con- 
tinues Mr.  Hamerton,  in  his  comments  on  this  anecdote, 
"  we  always  commit  one  of  two  mistakes — either  we  con- 
clude that  the  beasts  have  great  knowledge  because  they 
are  so  clever,  or  else  we  fancy  that  they  must  be  stupid 
because  they  are  so  ignorant."  "  The  main  difficulty  in 
conceiving  the  mental  states  of  animals,"  says  the  same 
observer,  "  is  that  the  moment  we  think  of  them  as  human, 
we  are  lost."  Yes,  but  the  pity  of  it  is  that  we  cannot 
think  of  them  in  any  other  terms  than  those  of  human 
consciousness.  The  only  world  of  constructs  that  we 
know  is  the  world  constructed  by  man. 

"  To  Newton  and  to  Newton's  dog,  Diamond,"  said 
Carlyle,  "  what  a  different  pair  of  universes  !  while  the 
painting  in  the  optical  retina  of  both  was  most  likely  the 
same."  Different,  indeed;  if  we  can  be  permitted,  without 
extravagance,  to  speak  of  the  universe  as  existing  at  all  for 
Diamond,  or  allowed,  except  in  hyperbole,  to  set  side  by 
side  a  conception  of  ultimate  generality,  like  the  universe, 
the  summation  of  all  conceptions,  and  "  the  painting  in 
the  optical  retina."  Carlyle's  meaning  is,  however,  clear 
enough.  Given  two  different  minds  and  the  same  facts, 
how  different  are  the  products !  In  the  construct  formed 
on  sight  of  the  simplest  object,  we  give  far  more  than  we 
receive ;  and  what  we  give  is  a  special  resultant  of 
inheritance  and  individual  acquisition.  No  two  of  us  give 
quite  the  same  in  amount  or  in  quality.  It  is  not  too 
much  to  say  that  for  no  two  human  beings  is  the  world  we 
live  in  quite  the  same.  And  if  this  be  so  of  human-folk, 
how  different  must  be  the  world  of  man  from  the  world 


336  Animal  Life  and  Intelligence. 

of   the    dog — the   world   of  Newton   from  the    world    of 
Diamond ! 

And  we  must  remember  that  it  is  not  merely  that  the 
same  world  is  differently  mirrored  in  different  minds,  but 
that  they  are  two  different  worlds.  If  there  is  any  truth 
in  what  I  have  urged  in  the  last  chapter,  we  construct  the 
world  that  we  see.  The  sensations  are,  as  we  have  seen, 
mental  facts,  in  no  sense  resembling  their  causes,  but 
representing  them  in  mental  symbolism.  Percepts  are  the 
elaborated  products  of  this  mental  symbolism.  The 
question,  then,  is  not — How  does  the  world  mirror  itself  in 
the  mind  of  the  dog  ?  but  rather — How  far  does  the  symbolic 
world  of  the  dog  resemble  the  symbolic  world  of  man  ? 
How  far  is  his  symbolism  the  same  as  ours  ?  Only  \>y 
fully  grasping  the  fact  that  the  external  world  of  objects 
does  not  exist  independently  of  us  (though  something 
exists  which  we  thus  symbolize),  shall  we  realize  the  great- 
ness of  the  difficulty  which  stands  in  the  path  of  the  student 
of  animal  psychology.  So  long  as  we  are  content  to  accept 
John  Bunyan's  crude  analogy  of  the  gateways  of  sense,  the 
difficulty  is  comparatively  small.  There  is  the  outside 
world  self-existent  and  independent ;  a  knowledge  of  it 
comes  into  the  mind  through  the  five  gateways  of  sense — 
a  picture  of  it  through  the  eye-gate,  and  so  on.  The  dog 
has  also  five  similar  gateways.  The  world  for  him  is, 
therefore,  much  the  same  as  for  us.  But  this  is  not  a  true 
analogy.  The  world  we  see  around  us  is  a  joint  product 
of  an  external  existence,  the  independent  nature  of  which 
we  can  never  know,  and  the  human  mind.  It  is  something 
we  construct  in  mental  symbolism.  How  far  does  the  dog 
construct  a  similar  world?  The  answer  to  this  question 
must,  as  it  seems  to  me,  be  largely  speculative. 

And  what  help  have  we  towards  answering  it  ?  That 
afforded  by  the  theory  of  organic  evolution.  If  we  accept 
that  theory,  and  accept  also  the  view  that  mental  or 
psychical  products  are  the  inseparable  concomitants  of 
certain  organic  or  physiological  processes,  then  we  have  a 
basis  from  which  to  start.  That  basis  I  adopt. 


Mental  Processes  in  Animals.  337 

Unfortunately,  we  have  at  present  but  little  particular 
knowledge  of  the  correlation  of  psychical  and  physiological 
processes.  We  cannot,  by  the  dissection  of  a  brain,  draw 
much  in  the  way  of  valid  and  detailed  inference  as  to  the 
nature  of  the  psychical  processes  which  accompany  its 
physiological  action.  Fortunately,  however,  on  the  other 
hand,  there  are  certain  physical  manifestations  which  do 
aid  us,  and  that  not  a  little,  in  drawing  inferences  from 
the  physical  to  the  mental.  For  organisms  exhibit  certain 
activities,  and  from  these  activities  we  can  infer  to  some 
extent  the  character  of  the  mental  processes  by  which  they 
are  prompted.  We  are  wont,  in  observing  the  actions  of 
our  fellow-men,  to  draw  conclusions  (often,  alas  !  erroneous) 
as  to  the  mental  processes  which  accompany  them.  We 
are  ourselves  active,  and  we  are  immediately  conscious  of 
the  modes  of  consciousness  which  accompany  our  actions. 
Thus  the  activities  of  organisms  give  us  some  clue  to  their 
mental  processes,  and  it  is  through  observation  of  their 
physical  activities  that  we  gain  nearly  all  that  is  of  par- 
ticular value  concerning  the  mental  activities  of  animals. 
These  activities  we  shall  have  to  consider  more  fully  in  a 
future  chapter.  In  the  present  chapter  we  shall  consider 
them  only  so  far  as  they  give  us  information  concerning 
the  perceptual  world  (or  worlds)  of  animals,  and  the  nature 
of  the  inferences  which  we  may  suppose  animals  to  draw 
from  the  phenomena  which  fall  within  their  observation. 

I  think  that,  from  the  fundamental  identity  of  life-stuff, 
or  protoplasm,  in  all  forms  of  animal  life,  and  from  the 
observed  similarity  of  nerves  and  nerve-cells  when  nervous 
tissue  has  been  developed,  and  again  from  the  essential 
resemblance  of  life-processes  in  all  animal  organisms,  we 
are  justified  in  believing  that  mental  or  conscious  pro- 
cesses, when  they  emerge,  are  essentially  similar  in  kind. 
Exactly  when  they  do  emerge  in  the  ascending  branches 
of  the  great  tree  of  animal  life  it  is  exceedingly  difficult, 
if  not  quite  impossible,  to  determine.  And  it  is,  I  fancy, 
quite  impossible  for  us  so  to  divest  ourselves  of  the  com- 
plexity of  human  consciousness  as  to  imagine  what  the 

z 


338  Animal  Life  and  Intelligence. 

simplicity  of  the  emergent  consciousness  in  very  lowly 
organisms  is  like.  But  I  think  that  we  may  fairly  believe 
that  some  dim  form  of  discrimination  is  the  germ  from 
which  the  spreading  tree  of  mind  shall  develop.* 

I  assume,  then,  that,  granting  the  theory  of  evolution, 
the  early  stages  of  the  process  of  construction — discrimina- 
tion, localization,  and  outward  projection — are  the  same 
in  kind  throughout  the  whole  range  of  animal  life,  wherever 
we  are  justified  in  surmising  that  psychical  processes  occur, 
and  the  power  of  registration  and  revival  in  memory  has 
been  established.  As  will  be  gathered,  however,  from  what 
I  have  already  said,  I  hold  that  the  nature  of  the  con- 
structs produced  is  and  must  be  for  us  human-folk,  since 
we  are  human-folk,  to  a  large  extent  a  matter  of  specula- 
tion. Remembering  this,  then,  endeavouring  never  to  lose 
sight  of  it  for  a  moment,  let  us  consider  what  we  may 
fairly  surmise  concerning  the  constructs  and  the  process 
of  construction  in  animals. 

There  can  be  no  question  that  the  animals  nearest  us 
in  the  scale  of  life — the  higher  mammalia — form  constructs 
analogous  to,  if  not  closely  resembling,  ours.  I  do  not 
think  the  resemblance  can  be  in  any  sense  close,  seeing  to 
how  large  an  extent  our  constructs  are  literally  our  handi- 
work. For  though  in  many  animals  the  tongue  and  lips 
are  delicate  organs  of  touch — not  to  mention  the  trunk  of 
the  elephant — and  though  in  the  monkeys  and  many 
rodents  the  hands  are  used  for  grasping,  still  we  have  no 
reason  to  suppose  that  in  any  other  mammal  the  geome- 
trical sense  of  touch  plays  so  determining  a  part  in  the 
formation  of  constructs  as  in  man.  On  the  other  hand, 
in  the  dog  and  the  deer,  for  example,  not  only  must  the 
marvellously  acute  sense  of  smell  have  a  far  higher  sug- 

*  Or  perhaps  we  may  say,  in  the  language  of  analogy,  that  when  the 
germinal  psychoplasm  of  some  dim  form  of  organic  memory  is  fertilized  by 
the  union  therewith  of  the  more  active  male  element  of  discrimination,  a 
process  of  segmentation  of  the  psychoplasm  sets  in  by  which,  in  process  of 
differentiation,  the  tissues  and  organa  of  the  mind  are  eventually  developed. 


Mental  Processes  in  Animals.  339 

gestive  value,  but  smells  and  odours  must,  one  would 
suppose,  be  built  into  the  constructs  in  a  far  larger  pro- 
portion. But  although  their  constructs  may  not  closely 
resemble  ours,  the  constructs  of  animals  may,  I  believe, 
be  fairly  regarded  as  closely  analogous  to  our  own.  And 
as  with  us,  so  with  them,  a  comparatively  simple  and 
meagre  suggestion  may  give  rise,  through  association  in 
experience,  to  the  construction  of  a  complex  object.  And 
again,  as  with  us,  so  with  them,  the  suggested  construct 
may  be  very  vague  and  indefinite. 

A  dog,  for  example,  is  lying  asleep  upon  the  mat,  and 
hears  an  unfamiliar  step  in  the  porch  without.  There  can 
be  no  question  that  this  suggests  the  construct  man.  But 
from  the  very  nature  of  the  case,  this  must  be  vague  and 
indefinite.  So,  too,  when  a  chamois,  bounding  across  the 
snow-fields,  stops  suddenly  when  he  scents  the  distant  foot- 
prints of  the  mountaineer,  the  construct  that  he  forms 
cannot  be  in  any  way  particularized — no  more  par- 
ticularized than  is  to  me  the  sheep  that  I  hear  bleating 
in  the  meadow  behind  yonder  wall. 

And  no  one  is  likely  to  question  the  fact  that  animals 
habitually  proceed  from  this  first  stage — the  formation  of 
constructs  by  immediate  association — to  the  second  stage 
of  construction — the  defining  of  constructs  by  examination. 
In  many  of  the  deer  tribe,  notably  the  prong-horn  of 
America,  this  tendency  is  so  strongly  developed  that  they 
may  be  lured  to  their  destruction  by  setting  up  a  strange 
and  unfamiliar  object  which,  as  we  put  it,  may  excite  their 
curiosity.  A  strange  noise  or  appearance  will  make  a  dog 
uneasy  until  he  has  by  examination  satisfied  himself  of 
the  nature  of  that  which  produces  it.  Of  this  an  instance 
fell  under  my  observation  a  few  days  ago.  My  cat  was 
asleep  on  a  chair,  and  my  little  son  was  blowing  a  toy 
horn.  The  cat,  without  moving,  mewed  uneasily.  I  told 
my  boy  to  continue  blowing.  The  cat  grew  more  uneasy, 
and  at  last  got  up,  stretched  herself,  and  turned  towards 
the  source  of  discomfort.  She  stood  looking  at  my  boy  for 
a  minute  as  he  blew.  Then  curling  herself  up,  she  went 


34-O  Animal  Life  and  Intelligence. 

to  sleep  again,  and  no  amount  of  blowing  disturbed  her 
further.  Similarly,  Mr.  Romanes's  dog  was  cowed  at  the 
sound  of  apples  being  shot  on  to  the  floor  of  a  loft  above 
the  stable ;  but  when  he  was  taken  to  the  place,  and  saw 
what  gave  rise  to  the  sound,  he  ceased  to  be  disquieted  by 
it.  Every  one  must  have  seen  animals  defining  their 
constructs  by  examination.  A  monkey  will  spend  hours 
in  the  examination  of  an  old  bottle  or  a  bit  of  looking- 
glass.  At  the  Zoological  Gardens  connected  with  the 
National  Museum  at  Washington,  a  monkey  was  observed 
with  a  female  opossum  on  his  knee.  He  had  discovered 
the  slit-like  opening  of  the  marsupial  pouch,  and  took  out 
first  one  and  then  another  of  the  young,  looked  them  over 
carefully,  and  replaced  them  without  injury.* 

There  may  possibly  be  some  difference  of  opinion  as  to 
whether  animals  are  able  to  infuse  into  their  constructs 
of  other  animals  the  element  of  feeling.  One  would,  per- 
haps, fain  believe  that  the  beasts  of  prey  were  wholly 
unaware  of  the  pain  they  inflict  on  other  organisms.  But 
I  question  whether  any  close  observer  of  animals  could 
hold  this  view.  Even  if  it  were  supposed  that  when  two 
dogs  fight  they  are  blind  to  the  pain  they  are  inflicting  on 
each  other,  their  mock-fighting  seems  to  imply  a  con- 
sciousness of  the  pain  they  might  inflict,  but  avoid  inflict- 
ing. And  many  of  us  have  presumably  had  experiences 
analogous  to  the  following:  A  favourite  terrier  of  mine 
was  once  brought  home  to  me  so  severely  gashed  in  the 
abdominal  region  that  I  felt  it  necessary  to  sew  up  the 
wound.  In  his  pain  the  poor  dog  turned  round  and  seized 
my  hand,  but  he  checked  himself  before  the  teeth  had 
closed  upon  me  tightly,  and  piteously  licked  my  hand. 
For  myself,  I  cannot  doubt  that  animals  project  into  each 
other  the  shadows  of  the  feelings  of  which  they  are  them- 
selves conscious. 

The  fact  that  dogs  may  be  deceived  by  pictures  f  shows 
that  they  may  be  led  through  the  sense  of  sight  to  form 

*  Nature,  vol.  xxxviii.  p.  257. 

t  For  examples,  see  Romanes's  "  Animal  Intelligence,"  p.  455. 


Mental  Processes  in  Animals.  341 

false  constructs,  that  is  to  say,  constructs  which  examina- 
tion shows  to  be  false.  Through  my  friend  and  colleague, 
Mr.  A.  P.  Chattock,  I  am  able  to  give  a  case  in  point.  I 
quote  from  a  letter  received  by  Mr.  Chattock:  "Your 
father  asks  me  to  tell  you  about  our  old  spaniel  Dash  and 
the  picture.  I  remember  it  well,  though  it  must  be  some- 
where about  half  a  century  ago.  We  had  just  unpacked 
and  placed  on  the  old  square  pianoforte,  which  then  stood 
at  the  end  of  the  dining-room,  the  well-known  print  of 
Landseer's  'A  Distinguished  Member  of  the  Humane 
Society.'  When  Dash  came  into  the  room  and  caught 
sight  of  it,  he  rushed  forward,  and  jumped  on  the  chair 
which  stood  near,  and  then  on  the  pianoforte  in  a  moment, 
and  then  turned  away  with  an  expression,  as  it  seemed  to 
us,  of  supreme  disgust." 

I  think  we  may  say,  then,  that  the  higher  animals  are 
able  to  proceed  a  long  way  in  the  formation  and  definition 
of  highly  complex  constructs  analogous  to,  but  probably 
differing  somewhat  from,  those  which  we  form  ourselves. 
These  constructs,  moreover,  through  association  with  re- 
constructs or  representations,  link  themselves  in  trains,  so 
that  a  sensation  or  group  of  sensations  may  suggest  a 
series  of  reconstructs  or  a  series  of  remembered  phenomena. 
We  here  approach  the  question  of  inferences,  of  which 
more  anon.  But  in  this  connection  passing  reference  may 
be  made  to  the  phenomena  of  dreaming.  Dogs  and  some 
other  animals  undoubtedly  seem  to  dream. 

The  nature  of  dreaming  may,  perhaps,  be  best  illustrated 
by  a  rough  analogy.  Professor  Clifford  likened  the  human 
consciousness  to  a  rope  made  up  of  a  great  number  of 
occasionally  interlacing  strands.  Let  us  picture  such  a 
rope  floating  in  water.  Much  of  it  is  submerged;  only 
the  upper  part  is  visible  at  the  surface.  This  upper  part 
is  like  the  series  of  mental  phenomena  of  which  we  are 
distinctly  conscious.  Below  this  lie  other  series  in  the 
half-submerged  state  of  subconsciousness.  Deeper  still  lie 
unconscious  physiological  processes  capable  of  emerging 
into  the  shadow  of  subconsciousness  or  the  light  of  distinct 


342  Animal  Life  and  Intelligence. 

consciousness.  Now  picture  this  rope  gradually  slipping 
round  as  it  floats,  so  that  now  one  part,  now  another,  sees 
the  light.  This  is  analogous  to  the  musing  state,  when 
we  allow  our  thoughts  to  wander  unchecked  by  any  effort 
of  attention.  Attention  is  the  faculty  by  which  we  steady 
the  rope,  so  that  one  particular  strand  is  kept  continuously 
uppermost.  The  inattentive  mind  is  one  in  which  the  rope 
keeps  slipping  round  and  refuses  to  be  steadied  in  this 
manner ;  and  in  unquiet  sleep,  when  the  faculty  of  attention 
is  dormant,  the  strands  come  quite  irregularly  and  hap- 
hazard to  the  surface,  and  we  have  the  phantasmagoria  of 
dreams. 

In  the  dog  or  the  ape  the  rope  is  presumably  in- 
comparably simpler.  But  that  it  is  of  the  nature  of  a  rope 
we  may,  perhaps,  not  improbably  surmise.  Interest  and 
the  attention  it  commands  steady  the  rope.  Animals 
differ  widely  in  their  power  of  attention,  as  every  one 
knows  who  has  endeavoured  to  educate  his  pets.  Darwin 
tells  us  that  those  who  buy  monkeys  from  the  Zoological 
Gardens,  to  teach  them  to  perform,  will  give  a  higher  price 
if  they  are  allowed  a  short  time  in  which  to  select  those  in 
which  the  power  of  attention  is  most  developed.  And 
when  animals  dream,  their  consciousness-rope  is  slipping 
round  unsteadily.  That  they  do  apparently  dream  is, 
so  far,  evidence  of  their  possessing  linked  chains  of 
memories. 

In  speaking  of  the  faculty  of  attention  in  animals,  it 
may  be  well  to  note  that  attention  is  of  two  kinds — per- 
ceptual or  direct,  and  conceptual  or  indirect.  In  perceptual 
attention  its  motive  is  directly  suggested  by  the  object 
which  stimulates  this  concentration  of  the  faculties;  a 
menacing  dog,  for  example,  stimulates  my  perceptual 
attention.  In  conceptual  attention  the  motive  is  ulterior 
and  indirect.  The  concentrated  attention  which  a  man 
devotes  to  the  acquisition  of  Sanscrit  does  not  arise  directly 
out  of  the  symbols  over  which  he  pores ;  it  is  of  intellectual 
origin. 

In  the  normal  life  of  animals  the  attention  is  of  the 


Mental  Processes  in  Animals.  343 

perceptual  order ;  it  is  a  direct  stimulation  of  the  faculties 
through  a  perceptual  presentation  of  sense  or  representa- 
tion in  memory  which  gives  rise  to  an  appetence  or  aver- 
sion. The  importance  of  such  a  faculty  is  obvious.  As 
M.  Eibot  well  says,  it  is  no  less  than  a  condition  of  life. 
The  carnivorous  animal  that  had  not  its  attention  roused 
on  sight  of  prey  would  stand  but  a  poor  chance  of  survival ; 
the  prey  that  had  not  its  attention  roused  by  the  approach 
of  its  natural  enemy  would  stand  but  a  poor  chance  of 
escape.  The  emperor  moth  that  had  not  its  attention 
roused  by  the  scent  of  the  virgin  female  would  stand  but  a 
poor  chance  of  propagating  its  species. 

We  are  not,  however,  at  present  in  a  position  further  to 
discuss  this  matter.  For  there  is  a  factor  in  the  process 
which  we  shall  have  to  consider  more  fully  hereafter — the 
emotional  factor.  The  hungry  lion  is  in  a  very  different 
position,  so  far  as  attention  is  concerned,  from  the  satiated 
animal.  The  force  and  volume  of  the  attention  depends 
not  merely,  or  even  mainly,  upon  the  intensity  of  the 
stimulus,  but  on  the  emotional  state  of  the  recipient 
organism. 

Endeavour  to  divert  the  attention  of  any  animal  which 
is  intent  upon  some  action  connected  with  the  main  busi- 
ness of  its  life — nutrition,  self-defence,  or  the  propaga- 
tion of  the  species — the  force  of  attention  will  at  once  be 
obvious. 

In  the  training  of  animals  (and  young  children)  artificial 
associations,  pleasurable  or  painful,  have  to  be  established 
in  connection  with  certain  actions.  Abnormal  appetences 
and  aversions  have  to  be  introduced  into  the  mental  con- 
stitution. In  this  process  much  depends  on  the  plasticity 
of  the  constitution.  In  the  absence  of  such  plasticity  it  is 
impossible  to  establish  new  associations. 

We  have  seen  that  words  are  arbitrary  *  symbols,  which 
we  associate  with  objects,  or  qualities,  or  actions.  Can 
animals,  we  may  ask,  form  such  arbitrary  associations  ? 

*  I  use  the  word  "  arbitrary  "  in  the  sense  that  they  form  no  part  of  the 
normal  construct  such  as  would  be  formed  by  the  animal. 


344  Animal  Life  and  Intelligence. 

There  can  be  little  question  that  they  can.  Many  of  the 
higher  animals  understand  perfectly  some  of  our  words. 
The  word  "cat"  or  "rats"  will  suggest  a  construct  to 
the  dog  on  which  he  may  take  very  vigorous  action.  How 
far  they  are  able  to  communicate  with  each  other  is  a 
somewhat  doubtful  matter.  But  the  signs  by  which  such 
communication  is  effected  are  probably  far  less  arbitrary. 
And,  in  any  case,  the  communication  would  seem  to 
refer  only  to  the  here  and  the  now.  A  dog  may  be 
able  to  suggest  to  his  companion  the  fact  that  he  has 
descried  a  worriable  cat ;  but  can  a  dog  tell  his  neigh- 
bour of  the  delightful  worry  he  enjoyed  the  day  before 
yesterday  ? 

I  imagine  that  what  a  dog  can  suggest  to  his  neigh- 
bour is  what  we  symbolize  by  the  simple  expression 
"  Come."  But  I  am  fully  aware  that  other  observers  will 
interpret  the  facts  in  a  different  way.  Here  is  an  anecdote 
that  is  communicated  to  me  by  Mr.  Eobert  Hall  Warren, 
of  Bristol.  "  My  grandfather,"  he  says,  "  a  merchant  of 
this  city,  or,  as  Thomas  Poole,  of  Stowey,  would  have 
preferred  calling  him,  '  a  tradesman,'  had  two  dogs,  one  a 
small  one  and  another  larger,  who,  being  fierce,  rejoiced 
in  the  appropriate  name  of  Boxer.  On  one  of  his  business 
journeys  into  Cornwall  he  took  the  smaller  dog  with  him, 
and  for  some  reason  left  it  at  an  inn  in  Devonshire, 
promising  to  call  for  him  on  his  return  from  Cornwall. 
When  he  did  so,  the  landlord  apologized  for  the  absence  of 
the  dog,  and  said  that,  some  time  after  my  grandfather 
left,  the  little  dog  fought  with  the  landlord's  dog,  and 
came  off  much  the  worse  for  the  fight.  He  then  dis- 
appeared, and  some  time  afterwards  returned  with  another 
and  larger  dog,  who  set  upon  his  enemy,  and,  I  think, 
killed  him.  Then  the  two  dogs  walked  off,  and  were  no 
more  seen.  From  the  description  given,  my  grandfather 
had  no  doubt  that  the  larger  dog  was  Boxer,  and,  on 
returning  home,  found  that  the  little  dog  had  come  back, 
and  that  both  dogs  had  gone  away,  and,  after  a  time,  had 
returned  home,  where  he  found  them."  Now,  some  will 


Mental  Processes  in  Animals.  345 

say  that  the  little  dog  told  Boxer  all  about  it ;  but  I  am 
inclined  to  believe  that  the  facts  may  be  explained  by  the 
communication  "  Come." 

Dogs  can  also  communicate  their  wishes  to  us.  The 
action  of  begging  in  dogs  is  a  mode  of  communication  with 
us.  Mr.  Eomanes  tells  of  a  dog  that  was  found  opposite  a 
rabbit-hutch  begging  for  rabbits.  When  I  was  at  the 
Diocesan  College  near  Capetown,  a  retriever,  Scamp, 
used  to  come  in  and  sit  with  the  lecturers  at  supper.  He 
despised  bread,  but  used  to  get  an  occasional  bone,  which 
he  was  not,  however,  allowed  to  eat  in  the  hall.  He  took 
it  to  the  door,  and  stood  there  till  it  was  opened  for  him. 
On  one  occasion  he  heard  without  the  excited  barking  of 
the  other  dogs.  He  trotted  round  the  hall,  picked  up  a 
piece  of  bread  which  one  of  the  boys  had  dropped,  and 
stood  with  it  in  his  mouth  at  the  door.  When  it  was 
opened,  he  dropped  the  bread,  and  raced  off  into  the 
darkness  to  join  in  the  fun.  In  a  similar  way,  but  with 
less  marked  intelligence,  I  have  seen  a  dog  begging  before 
a  door  which  he  wished  opened.  My  cat  has  been  taught 
to  touch  the  handle  of  the  door  with  his  paw  when  he 
wishes  to  leave  the  room.  Mr.  Arthur  Lee,  of  Bristol, 
tells  me  that  a  favourite  cat  has  a  habit  of  knocking  for 
admittance  by  raising  the  door-mat  and  letting  it  fall. 
This  is  an  action  similar  to  those  communicated  by  several 
observers  to  Nature,  where  cats  have  learnt  either  to  knock 
for  admittance  or  to  ring  the  bell — an  action  which,  as  my 
friend,  Mr.  J.  Clifton  Ward,  informed  me,  was  also  per- 
formed by  a  dog  of  his.  I  think,  therefore,  that  it  is 
unquestionable  that  the  higher  animals  are  able  to  associate 
arbitrary  signs  with  certain  objects  and  actions,  and  to 
build  these  signs  into  the  constructs  that  they  form.  Sir 
John  Lubbock  has  tried  some  experiments  with  his  in- 
telligent black  poodle  Van,  with  the  object  of  ascertaining 
how  far  the  dog  could  be  taught  to  communicate  his  wishes 
by  means  of  printed  cards.  "I  took,"  he  says,*  "two 
pieces  of  cardboard,  about  ten  inches  by  three,  and  on  one 
*  «<  The  Senses  of  Animals,"  p.  277. 


346  Animal  Life  and  Intelligence. 

of  them  printed  in  large  letters  the  word  '  FOOD,'  leaving 
the  other  blank.  I  then  placed  the  two  cards  over  two 
saucers,  and  in  the  one  under  the  '  Food  '  card  put  a  little 
bread-and-milk,  which  Van,  after  having  his  attention 
called  to  the  card,  was  allowed  to  eat.  This  was  repeated 
over  and  over  again  till  he  had  had  enough.  In  about  ten 
days  he  began  to  distinguish  between  the  two  cards.  I 
then  put  them  on  the  floor,  and  made  him  bring  them  to 
me,  which  he  did  readily  enough.  When  he  brought  the 
plain  card,  I  simply  threw  it  back ;  while,  when  he  brought 
the  '  Food '  card,  I  gave  him  a  piece  of  bread,  and  in  about 
a  month  he  had  pretty  well  learned  to  realize  the  difference. 
I  then  had  some  other  cards  printed  with  the  words  *  Out/ 
'  Tea,'  '  Bone,'  '  Water,'  and  a  certain  number  also  with 
words  to  which  I  did  not  intend  him  to  attach  any  sig- 
nificance, such  as  '  Nought,'  '  Plain,'  '  Ball,'  etc.  Van  soon 
learned  that  bringing  a  card  was  a  request,  and  soon 
learned  to  distinguish  between  the  plain  and  printed  cards  ; 
it  took  him  longer  to  realize  the  difference  between  words, 
but  he  gradually  got  to  recognize  several,  such  as  '  Food,' 
'Out,'  'Bone,'  'Tea,'  etc.  If  he  was  asked  whether  he 
would  like  to  go  out  for  a  walk,  he  would  joyfully  fish 
up  the  '  Out '  card,  choosing  it  from  several  others,  and 
bring  it  to  me  or  run  with  it  in  evident  triumph  to  the 
door. 

"A  definite  numerical  statement  always  seems  to  me 
clearer  and  more  satisfactory  than  a  mere  general  assertion. 
I  will,  therefore,  give  the  actual  particulars  of  certain  days. 
Twelve  cards  were  put  on  the  floor,  one  marked  '  Food ' 
and  one  '  Tea.'  The  others  had  more  or  less  similar 
words.  I  may  again  add  that  every  time  a  card  was 
brought,  another  similarly  marked  was  put  in  its  place. 
Van  was  not  pressed  to  bring  cards,  but  simply  left  to  do 
as  he  pleased.* 

*  As  I  understand  the  observations  here  tabulated,  the  twelve  cards  lay 
always  within  Van's  reach  and  sight.  An  ordinary  untrained  dog  would  have 
taken  no  notice  of  them.  But  Van,  when  he  wanted  food  or  tea,  went  and 
fetched  the  appropriate  card,  and  got  what  he  wanted  in  exchange.  In  twelve 
days  he  only  made  two  mistakes,  bringing  "  Nought "  once  and  "  Door  "  once. 


Mental  Processes  in  Animals.  347 


Day  1.  Van  brought  •  Food '  4  times,  '  Tea'  2  times. 
»    2-  »,  »  6     „ 

»    3.  „  „  8     „ 

,,4.  7      , 


5.  „  „  6 

6.  „  „  6 

7.  „  „  8 

5 
4 

10. 


11. 
12. 


4     „ 

3     „        '  Nought  *  once. 


10     „          „      4     „          '  Door '  once. 
10     „          „      3     „ 
6      ,  ,      3     , 


31 


"  Thus,  out  of  113  times,  he  brought  'Food'  80  times, 
1  Tea '  31  times,  and  [one  out  of]  the  other  10  cards  only 
twice.  Moreover,  the  last  time  he  was  wrong  he  brought 
a  card — namely, '  Door ' — in  which  three  letters  out  of  four 
were  the  same  as  in  '  Food.'  " 

These  experiments  and  observations  are  of  great 
interest.  But,  of  course,  no  stress  whatever  must  be  laid 
on  the  fact  that  words  chanced  to  be  printed  on  the  cards 
instead  of  any  other  arrangements  of  lines.  I  draw 
attention  to  this  because  I  have  heard  Sir  John  Lubbock's 
interesting  experiments  quoted,  in  conversation,  as  evidence 
that  the  dog  understands  the  meaning  of  words,  not  only 
spoken,  but  written  !  What  they  show  is  that  Van  is  able, 
under  human  guidance,  to  associate  certain  arbitrary 
symbols  with  certain  objects  of  appetence ;  and,  desiring 
the  object,  will  bring  its  symbol.  It  would  have  been 
better,  I  think,  because  less  misleading  to  the  general 
public,  had  Sir  John  Lubbock  selected  other  arbitrary 
symbols  than  the  printed  words  we  employ.  Then  no  one 
could  have  run  away  with  the  foolish  notion  that  the  dog 
understands  the  meaning  of  these  words.  No  doubt  if  they 
had  been  written  in  Greek  or  Hebrew,  some  people  would 
have  been  interested,  but  not  surprised,  to  learn  that  a 
dog  can  be  taught  to  understand  with  perfect  ease  these 


The  next   question  is — Have  the   higher   animals  the 
power  of  analyzing  their  constructs  and  forming  isolates  or 


348  Animal  Life  and  Intelligence. 

abstract  ideas  of  qualities  apart  from  the  constructs  of 
•which  these  qualities  are  elements  ?  Can  we  say,  with 
Mr.  Romanes,*  "All  the  higher  animals  have  general 
ideas  of  '  good-for-eating  '  and  '  not-good-for-eating,'  quite 
apart  from  any  particular  objects  of  which  either  of  these 
qualities  happens  to  be  characteristic "  ?  Or  with  Leroy,t 
that  a  fox  "will  see  snares  when  there  are  none;  his 
imagination,  distorted  by  fear,  will  produce  deceptive 
shapes,  to  which  he  will  attach  an  abstract  notion  of 
danger  " ? 

Now,  this  is  a  most  difficult  question  to  answer.  But 
it  seems  to  me  that,  if  we  take  the  term  "  abstract  idea  "  in 
the  sense  in  which  I  have  used  the  word  "  isolate,"  we 
must  answer  it  firmly,  but  not  dogmatically  (this  is  the 
last  subject  in  the  world  on  which  to  dogmatize),  in  the 
negative.  Fully  admitting,  nay,  contending,  that  this  is  a 
matter  in  which  it  is  exceedingly  difficult  to  obtain  anything 
like  satisfactory  evidence,  I  fail  to  see  that  we  have  any 
grounds  for  the  assertion  that  the  higher  animals  have 
abstract  ideas  of  "good-for-eating"  or  "not-good-for- 
eating,"  quite  apart  from  any  particular  objects  of  which 
either  of  these  qualities  happens  to  be  characteristic.  J 

The  particular  example  is  well  chosen,  since  the  idea  of 
food  is  a  dominant  one  in  the  mind  of  the  brute.  There 
can  be  no  question  that  the  quality  of  eatability  is  built  in 
by  the  dog  into  a  great  number  of  his  constructs.  But  I 
question  whether  this  quality  can  be  isolated  by  the  dog, 
and  can  exist  in  his  mind  divorced  from  the  eatables  which 
suggest  it.  If  it  can,  then  the  dog  is  capable  of  forming  a 
concept  as  I  have  defined  the  term.  I  can  quite  understand 

*  "  Mental  Evolution  in  Man,"  p.  27. 

t  "Intelligence  of  Animals,"  p.  121. 

J  Mr.  Romanes  also  says  ("Mental  Evolution  in  Animals,"  p.  235), 
"  This  abstract  idea  of  ownership  is  well  developed  in  many  if  not  in  most 
dogs."  By  an  abstract  idea  of  ownership  I  understand  a  conception  of  owner- 
ship which,  to  modify  Mr.  Romanes's  phrase,  is  quite  apart  from  any  objects 
or  persons  of  which  such  ownership  happens  to  be  characteristic.  Even  if  we 
believe  that  a  dog  can  regard  tliis  or  that  man  as  his  owner,  or  this  or  that 
object  as  his  master's  property,  still  even  this  seems  to  me  a  very  different 
thing  from  his  possessing  an  abstract  idea  of  ownership. 


Mental  Processes  in  Animals.  349 

that  a  hungry  dog,  prowling  around  for  food,  has,  sug- 
gested by  his  hunger,  vague  representations  in  memory 
of  things  good  to  eat,  in  which  the  element  of  eatability  is 
predominant  and  comparatively  distinct,  while  the  rest  is 
vague  and  indistinct.  And  that  this  is  a  concept  in  Mr. 
Sully's  use  of  the  term,  I  admit.  But  it  appears  to  me 
that  there  is  a  very  great  difference  between  a  perceptual 
construct  with  eatability  predominant  and  the  rest  vague, 
and  a  conceptual  isolate  or  abstract  idea  of  eatability  quite 
apart  from  any  object  or  objects  of  which  this  quality  is 
characteristic.  And  to  mark  the  difference,  I  venture  to 
call  the  prominent  quality  a  predominant  as  opposed  to 
the  isolate  when  the  quality  is  floated  off  from  the  object. 
No  doubt  it  is  out  of  this  perceptual  prominence  of  one 
characteristic  and  vagueness  of  its  accompaniments  that  con- 
ceptual isolation  of  this  one  characteristic  has  grown,  as  I 
believe,  through  the  naming  of  predominants.  But  I  should 
draw  the  line  between  the  one  and  the  other  somewhere 
distinctly  above  the  level  of  intelligence  that  is  attained  by 
any  dumb  animal.  I  am  not  prepared  either  to  affirm  or 
deny  that  this  line  should  be  drawn  exactly  between  brute 
intelligence  and  human  intelligence  and  reason,  though  I 
strongly  incline  to  the  view  that  it  should.  I  am  not  sure 
that  every  savage  and  yokel  is  capable  of  isolation,  that  he 
raises  the  predominant  to  the  level  of  the  isolate,  or  abstract 
idea.  I  am  not  sure  that  these  simple  folk  submit  the 
phenomena  of  nature  around  them,  and  of  their  own 
mental  states  to  analysis.  But  they  have  in  language  the 
instrument  which  can  enable  them  to  do  so,  even  if 
individually  some  of  them  have  not  the  faculty  for  using 
language  for  this  purpose.  That  is,  however,  a  different 
question.  But  I  do  not  at  present  see  satisfactory  evidence 
of  the  fact  that  animals  form  isolates,  and  I  think  that  the 
probability  is  that  they  are  unable  to  do  so.  I  am,  there- 
fore, prepared  to  say,  with  John  Locke,  that  this  abstraction 
"is  an  excellency  which  the  faculties  of  brutes  do  by  no 
means  attain  to." 

I  am  anxious,  however,  not  to  exaggerate  my  divergence, 


350  Animal  Life  and  Intelligence. 

more  apparent,  I  believe,  than  real,  from  so  able  a  student 
of  animal  psychology  as  Mr.  Eomanes.  Let  me,  therefore, 
repeat  that  it  is  the  power  of  analysis — the  power  of 
isolating  qualities  of  objects,  the  power  of  forming  "  abstract 
ideas  quite  apart  from  the  particular  objects  of  which  the 
particular  qualities  happen  to  be  characteristic,"  as  I 
understand  these  words — that  I  am  unable  to  attribute  to 
the  brute.  Animals  can  and  do,  I  think,  form  pre- 
dominants  ;  they  have  not  the  power  of  isolation. 

Furthermore,  it  seems  to  me  that  this  capacity  of 
analysis,  isolation,  and  abstraction  constitutes  in  the 
possessor  a  new  mental  departure,  which  we  may  describe 
as  constituting,  not  merely  a  specific,  but  a  generic  differ- 
ence from  lower  mental  activities.  I  am  not  prepared, 
however,  to  say  that  there  is  a  difference  in  kind  between 
the  mind  of  man  and  the  mind  of  the  dog.  This  would  imply 
a  difference  in  origin  or  a  difference  in  the  essential  nature 
of  its  being.  There  is  a  great  and  marked  difference  in  kind 
between  the  material  processes  which  we  call  physiological 
and  the  mental  processes  we  call  psychical.  They  belong 
to  wholly  different  orders  of  being.  I  see  no  reason  for 
believing  that  mental  processes  in  man  differ  thus  in  kind 
from  mental  proceses  in  animals.  But  I  do  think  that  we 
have,  in  the  introduction  of  the  analytic  faculty,  so  definite 
and  marked  a  new  departure  that  we  should  emphasize  it 
by  saying  that  the  faculty  of  perception,  in  its  various 
specific  grades,  differs  generically  from  the  faculty  of  con- 
ception. And  believing,  as  I  do,  that  conception  is  beyond 
the  power  of  my  favourite  and  clever  dog,  I  am  forced  to 
believe  that  his  mind  differs  generically  from  my  own. 

Passing  now  to  the  other  vertebrates,  the  probabilities 
are  that  their  perceptual  processes  are  essentially  similar 
to  those  of  the  higher  animals  ;  but,  in  so  far  as  these 
creatures  differ  more  and  more  widely  from  ourselves,  we 
may,  perhaps,  fairly  infer  that  their  constructs  are  more 
and  more  different  from  ours.  Still,  the  thrush  that  listens 
attentively  on  the  lawn  and  hops  around  a  particular  spot 


Mental  Processes  in  Animals.  351 

must  have  a  vague  construct  of  the  worm  he  hopes  to  have 
a  more  particular  acquaintance  with  ere  long.  The  cobra 
that  I  watched  on  the  basal  slopes  of  Table  Mountain,  and 
that  raised  his  head  and  expanded  his  hood  when  I  pitched 
a  pebble  on  to  the  granite  slope  over  which  he  was  gliding, 
must  have  had  a  vague  percept  suggested  thereby.  The 
trout  that  leaps  at  your  fly  so  soon  as  it  touches  the  water 
must  have  a  vague  percept  of  an  eatable  insect  which 
suggests  his  action.  The  carp  *  that  come  to  the  sound  of 
a  bell  must  have,  suggested  by  that  sound,  vague  percepts 
of  edible  crumbs.  And  no  one  who  has  watched  as  a  lad 
the  fish  swimming  curiously  round  his  bait  can  doubt  that 
they  are  by  examination  defining  their  percepts,  and  drawing 
unsatisfactory  inferences  of  a  perceptual  nature. 

And  here  let  us  notice  that  the  whole  set  of  phenomena 
which  have  been  described  in  previous  chapters  under  the 
heads  of  recognition-marks,  of  warning  coloration,  and  of 
mimicry,  involve  close  and  accurate  powers  of  perception. 
Eecognition-marks  are  developed  for  the  special  purpose 
of  enabling  the  organisms  concerned  rapidly  and  accurately 
to  form  particular  perceptual  constructs.  Of  what  use 
would  warning  coloration  be  if  it  did  not  serve  to  suggest 
to  the  percipient  the  disagreeable  qualities  with  which  it 
is  associated  ?  The  very  essence  of  the  principle  of  mimicry 
is  that  misleading  associations  are  suggested.  Here  a 
false  construct,  untrue  to  fact,  that  is  to  say,  one  that 
verification  would  prove  to  be  false,  is  formed ;  just  as  a 
well-executed  imitation  orange,  in  china  or  in  soap,  may 
lead  a  child  to  form  a  false  construct,  one  that  is  proved 
to  be  incorrect  so  soon  as  the  suggestions  of  sight  are 
submitted  ta  verification  by  touch,  smell,  and  taste. 

No  one  who  has  carefully  watched  the  habits  of  birds 
can  have  failed  to  notice  how  they  submit  a  doubtful  object 
to  examination.  Probably  the  avoidance  of  insects  pro- 
tected by  warning  colours  is  not  perfectly  instinctive.  I 

*  Doubt  has  recently  been  thrown  on  this  fact.  Mr.  Bateson  has  shown 
that  some  fishes  do  not  hear  well,  and  has  suggested  that  the  carp  may  be 
attracted  by  seeing  people  come  to  the  edge  of  the  pond. 


352  Animal  Life  and  Intelligence. 

have  seen  young  birds,  after  some  apparent  hesitation, 
peck  once  or  twice  doubtfully  at  such  insects.  A  young 
baboon  with  whom  I  experimented  at  the  Cape  seemed  to 
have  an  undefined  aversion  to  certain  caterpillars,  which 
he  could  not  be  induced  to  taste,  though  he  smelt  at  them. 
Scorpions  he  darted  at,  twisted  off  the  sting,  and  ate  with 
greedy  relish. 

If  nudibranchs  and  other  marine  invertebrates  be  pro- 
tectively coloured,  there  must  be  corresponding  perceptual 
powers  in  the  fishes  that  are  thus  led  to  avoid  them ;  for 
there  seems  to  be  definite  avoidance,  and  not  merely  in- 
difference. This,  however,  might  be  made  the  subject  of 
further  experiment,  not  only  with  fishes,  but  with  other 
animals.  I  tried  some  chickens  with  currant-moth  cater- 
pillars, to  each  of  which  I  tied  with  thread  a  large  looper. 
Some  of  them  would  have  nothing  to  do  with  the  unwonted 
combination.  But  one  persistently  pecked  at  the  looper, 
and  tried  to  detach  it  from  its  fellow-prisoner.  Though, 
on  the  whole,  there  was  some  tendency  for  aversion  to  the 
currant-moth  caterpillar  to  overmaster  the  appetence  for 
the  looper,  I  was  not  altogether  satisfied  with  the  result 
of  the  experiment.  But  I  think  that  if  the  protectively 
coloured  larva  had  been  regarded  with  mere  indifference 
(i.e.  neither  aversion  nor  appetence),  the  appetence  for 
the  loopers  should  have  made  the  chickens  seize  them  at 
once. 

To  return  to  fishes.  It  is  probably  difficult  or  impos- 
sible for  us  to  imagine  what  their  constructs  are  like ;  but 
that  they,  too,  proceed  to  define  them  by  examination 
seems  to  be  a  legitimate  inference  from  some  of  their 
actions.  Mr.  Bateson  says,  "  The  rockling  searches  [for 
food]  by  setting  its  filamentous  pelvic  fins  at  right  angles 
to  the  body,  and  then  swimming  about,  feeling  with  them. 
If  the  fins  touch  a  piece  of  fish  or  other  soft  body,  the 
rockling  turns  its  head  round  and  snaps  it  up  with  great 
quickness.  It  will  even  turn  round  and  examine  uneatable 
substances,  as  glass,  etc.,  which  come  in  contact  with  its 
fins,  and  which  presumably  seem  to  it  to  require  explana- 


Mental  Processes  in  Animals.  353 

tion."  *  And,  speaking  of  the  sole,  the  same  observer 
says,f  "  In  searching  for  food  the  sole  creeps  about  on 
the  bottom  by  means  of  the  fringe  of  fin-rays  with  which 
its  body  is  edged,  and,  thus  slowly  moving,  it  raises  its 
head  upwards  and  sideways,  and  gently  pats  the  ground 
at  intervals,  feeling  the  objects  in  its  path  with  the  peculiar 
viliform  papillae  which  cover  the  lower  (left)  side  of  its  head 
and  face.  In  this  way  it  will  examine  the  whole  surface 
of  the  floor  of  the  tank,  stopping  and  going  back  to  in- 
vestigate pieces  of  stick,  string,  or  other  objects  which  it 
feels  below  its  cheek." 

If  we  admit  the  fact  that  carp  come  to  be  fed  at  the 
sound  of  a  bell,  we  have  evidence  that  some  fishes  can 
associate  an  arbitrary  sound  with  the  advent  of  things 
good  to  eat.  But  it  is,  perhaps,  better  at  present  to  regard 
the  fact  as  one  requiring  verification. 

That  some  birds  can  associate  arbitrary  signs  with  their 
percepts  will  be  admitted  by  all  who  have  watched  their 
habits.  And  from  its  peculiar  and  almost  unique  power 
of  articulation,  the  parrot  shows  us  that  not  only  may  the 
words  suggest  a  construct,  but  that  the  sight  of  the  con- 
struct may  suggest  the  word  that  it  has  heard  associated 
with  the  object  by  man.  Mr.  Romanes  gives  evidence 
which  satisfies  him  that  a  parrot  which  had  associated  the 
word  "  bow-wow  "  with  a  particular  dog,  uttered  this  sound 
when  another  dog  entered  the  room.  The  word  was  here 
suggested  at  sight,  not  of  the  same  object,  but  of  an  object 
which  the  bird  recognized  as  similar.  A  somewhat  similar 
case  is  furnished  by  one  of  my  own  correspondents  (Miss 
Mabel  Westlake).  "  We  left  London,"  she  says,  "  in 
December,  1888,  and  brought  our  grey  parrot  with  us ;  but 
left  behind  with  a  friend  our  favourite  cat,  a  dark  tortoise- 
shell  with  a  white  breast,  the  forehead  clearly  marked  with 
a  division  down  the  middle  to  the  tip  of  the  nose.  This 
led  to  our  calling  her  'Demi.'  For  a  week  or  two  after 

*  Journal  of  Marine  Biological  Association,  New  Series,  vol.  i.   No.   2, 
p.  214.     I  should  not  myself  have  used  the  word  "  explanation." 
t  Ibid.  vol.  i.  No.  3,  p.  240. 

2A 


354  Animal  Life  and  Intelligence. 

our  arrival  in  Bristol,  a  black-and-white  cat  belonging  to 
the  people  formerly  living  here  frequented  the  house.  The 
parrot  seemed  delighted  to  see  this  cat,  which  was  larger 
than  our  old  cat,  and  called  it  Dem,  as  she  had  been 
accustomed  to  do  in  London.  From  that  time  until  the 
commencement  of  January  (1890),  which  was  over  a  year, 
the  parrot  had  not  seen  a  cat  that  we  are  aware  of,  nor 
had  we  heard  her  call  it  for  a  long  time.  About  six  weeks 
ago,  as  I  was  coming  along  Kingsdown  Parade,  a  large 
black  kitten  followed  me  home.  We  took  it  in  and  fed  it. 
The  next  day  it  came  into  the  room  where  the  parrot  was, 
and  she  immediately  said  '  Puss  !  puss  !  puss !  Hullo, 
dear  !  '  and  during  the  day  called  it  by  the  same  name, 
'  Dem !  Dem  !  Dem  !  '  that  she  had  called  our  cat  in 
London." 

We  may  here  notice  that,  in  most  of  the  tricks  which 
animals  are  taught  to  perform,  the  action  is  suggested  by 
a  form  of  words  (or  the  tone  and  manner  in  which  they 
are  uttered).  Mr.  John  G.  Naish,  J.P.,  of  Ilfracombe,* 
has  taught  his  cockatoo  the  following  trick  (I  quote  Mr. 
Naish's  own  words) :  "  I  give  him  a  shilling,  which  he  puts 
into  the  slit  of  a  money-box.  This  is  '  enlisting.'  After 
that,  I  say  to  him,  '  Will  you  die  for  the  queen,  like  a  loyal 
soldier  ?  '  Then  he  lies  on  his  back,  with  his  paws  together, 
for  as  long  as  I  hold  up  my  finger.  '  Now  live  for  your 
master ! '  He  takes  hold  of  my  finger  and  resumes  his 
erect  posture.  Last  year  I  took  him  into  the  street  near 
my  house,  and  collected  on  our  '  Hospital  Saturday.'  He 
worked  for  more  than  an  hour  before  he  became  impatient. 
And  then  he  would  do  no  more,  but,  flung  the  coins  over 
his  head  or  at  the  giver  in  the  funniest  way.  He  went  to 
sleep  for  a  long  time  after  that  performance  ;  and  when  he 
awoke  and  I  took  him,  he  covered  my  face  with  kisses,  as 
if  he  was  glad  to  find  his  bad  dream  was  over."  The 
weariness  and  failure  to  perform  the  trick  when  tired,  and 
the  long  sleep  which  succeeded,  are  interesting  points. 

*  I  have  to  thank  this  gentleman  for  a  most  interesting  account  of  the 
intelligence  of  his  favourite  bird. 


Mental  Processes  in  Animals.  355 

What  I  wish  especially  to  notice  is,  however,  that  the 
actions  are  suggested  by  certain  forms  of  words ;  but  that 
there  is  no  evidence  that  the  form  of  words  is  in  any  sense 
understood.  When  the  onlooker  sees  a  bird  lie  on  its  back 
when  asked  if  it  will  die  for  the  queen,  and  get  up  again 
when  told  to  live  for  its  master,  he  is  apt  to  think  that, 
since  he  understands  the  form  of  words,  the  bird  must 
understand  them  too.  But  I  am  convinced  that  Mr. 
Naish's  intelligent  cockatoo  could  have  been  taught  with 
equal  ease  to  lie  down  at  the  command  "Abracadabra," 
and  to  stand  up  again  at  "  Hocus  pocus."  Tricks  taught 
to  animals  involve  the  performing  animal  and  the  human 
onlooker.  The  form  of  words  introduced  is  for  the  sake  of 
the  latter,  not  for  the  sake  of  the  former. 

So  much  has  been  written  concerning  the  intelligence 
of  the  parrot,  and  so  much  has  been  said  concerning  its 
imitative  power  of  speech,  that  I  must  say  somewhat 
on  this  head.  I  have  received  from  Miss  Mildred  Sturge, 
of  Clifton,  an  interesting  account  of  an  African  West  Coast 
parrot  which  was  possessed  by  Miss  Tregelles,  of  Falmouth. 
This  parrot  used  the  phrases  it  had  learnt  appropriately  in 
time  and  place.  "  At  dinner,  when  he  saw  the  vegetable- 
dishes,  he  generally  said,  '  Polly  wants  potato  ; '  at  tea  he 
would  say,  'Polly  wants  cake,'  or  '  Polly's  sop,'  or  '  Polly's 
toast.'  Our  grandmother's  house  was  not  far  from  the 
station,  and  almost  before  people  could  hear  it,  Polly 
would  announce,  '  Grandmamma,  the  train  is  coming,'  and 
presently  the  train  would  quietly  go  by.  Besides  repeating 
much  poetry,  Polly  made  new  editions  by  putting  lines 
together  from  different  authors ;  but  the  remarkable  thing 
was  that  he  always  got  the  right  rhyme.  One  of  his 
favourite  mixtures  was,  '  Sing  a  song  of  sixpence '  and  '  I 
love  little  pussy.'  One  day  my  mother  overheard — 

"  '  Four  and  twenty  blackbirds, 

When  they  die, 
Go  to  that  world  above, 
Baked  in  a  pie. '  " 

Now,  we  must  not  underrate  nor  overrate  the  evidence 


356  Animal  Life  and  Intelligence. 

afforded  by  parrot-talk.  The  rhyme-association  is  interest- 
ing ;  but  since  we  cannot  suppose  that  the  poetry  is  more 
to  the  parrot  than  a  linked  series  of  sounds,  there  does  not 
seem  much  evidence  of  intelligence  here,  though  the 
evidence  of  memory  is  important.  The  correct  association 
of  words  and  phrases  with  appropriate  objects  and  actions 
is  of  great  interest.  But  the  fact  that  they  are  words  and 
phrases  does  not  give  them  a  higher  value  than  that  of 
imitative  actions  in  the  dog  or  other  animal.  What 
parrot-talk  does  give  us  evidence  of  is  (1)  remarkable 
powers  of  memory ;  (2)  an  almost  unique  power  of  articula- 
tion ;  (3)  a  great  faculty  of  imitation ;  (4)  and  some  in- 
telligence in  the  association  of  certain  linked  sounds  which 
we  call  phrases  with  certain  objects  or  actions.  The 
teaching  of  phrases  to  the  parrot  is  certainly  not  more 
remarkable  than  the  teaching  of  clever  tricks  to  many 
birds.  But  the  fact  that  word-sounds  are  articulated 
throws  a  glamour  over  these  special  tricks,  and  leads  some 
people  to  speak  of  the  parrot's  using  language,  instead  of 
saying  that  the  parrot  can  imitate  some  of  the  sounds 
made  by  man,  and  can  associate  these  sounds  with  certain 
objects. 

Coming  now  to  the  invertebrates,  much  has  been  written 
concerning  the  psychology  and  intelligence  of  ants  and 
bees.  What  shall  we  say  concerning  their  constructs  ? 
For  reasons  already  given,  I  think  we  may  suppose  that 
they  are  analogous  to  ours ;  but  it  can  scarcely  be  that 
they  in  any  way  closely  resemble  ours.  Their  sense-organs 
are  constructed  on  a  different  plan  from  ours ;  they  have 
probably  senses  of  which  we  are  wholly  ignorant.  Is  it 
conceivable,  by  any  one  who  has  grasped  the  principle  of 
construction,  that  with  these  differently  organized  senses 
and  these  other  senses  than  ours,  the  world  they  construct 
can  much  resemble  the  world  we  construct  ?  Eemember 
how  largely  our  perceptual  world  is  the  product  of  our 
geometrical  senses — of  our  delicate  and  accurate  sense  of 
touch,  and  of  our  binocular  vision,  with  its  delicate  and 


Mental  Processes  in  Animals. 


357 


accurate  muscular  adjustments.  Kemember  how  largely 
these  muscular  adjustments  enter  into  our  perceptual  world 
as  constructed  in  vision.  And  then  remember,  on  the 
other  hand,  that  the  bee  is  encased  in  a  hard  skin  (the 
chitinous  exoskeleton),  and  that  its  tactile  sensations  are 
mainly  excited  by  means  of  touch-hairs  seated  thereon. 
Remember  its  compound  eye  with  mosaic  vision,  coarser 
by  far  than  our  retinal  vision,  and  its  ocelli  of  proble- 
matical value,  and  the  complete  absence  of  muscular 
adjustment  in  either  the  one  or  the  other.  Can  we  con- 
ceive that,  with  organs  so  different,  anything  like  a  similar 
perceptual  world  can  be  elaborated  in  the  insect  mind  ?  I 
for  one  cannot.  Admitting,  therefore,  that  their  perceptions 
may  be  fairly  surmised  to  be  analogous,  that  their  world  is 
the  result  of  construction,  I  do  not  see  how  we  can  for  one 
moment  suppose  that  the  perceptual  world  they  construct 
can  in  any  accurate  sense  be  said  to  resemble  ours.  For 
all  that,  the  processes  of  discrimination,  localization,  out- 
ward projection ;  the  formation  of  vague  constructs,  their 
definition  through  experience,  and  the  association  of  re- 
constructs or  representations; — all  these  processes  are 
presumably  similar  in  kind  to  those  of  which  we  have 
evidence  in  ourselves. 

In  considering  such  organisms  as  ants  and  bees,  however, 
we  must  be  careful  to  avoid  the  error  of  supposing  that, 
because  they  happen  to  have  no  backbones,  they  are  neces- 
sarily low  in  the  scale  of  life  and  intelligence.  The  tree  of 
life  has  many  branches,  and,  according  to  the  theory  of 
evolution,  these  divergent  branches  have  been  growing  up 
side  by  side.  There  is  no  reason  whatever  why  the  bee  and 
the  ant,  in  their  branch  of  life,  should  not  have  attained  as 
high  a  development  of  structure  and  intelligence  as  the 
elephant  or  the  dog  in  their  branch  of  life.  I  do  not  say 
that  they  have.  As  it  is  difficult  to  compare  their  structure, 
in  complexity  and  efficiency,  with  that  of  vertebrates,  so  is 
it  difficult  to  compare  their  intelligence.  The  mere  matter 
of  size  may  have  necessitated  the  condensation  of  intelli- 
gence into  instinct  in  a  far  higher  degree  than  was  required 


358  Animal  Life  and  Intelligence. 

in  the  big-brained  mammals.  Still,  their  intelligence, 
though  of  a  different  order  and  on  a  different  plane,  may 
well  be  as  high.  And  Darwin  has  said  that  the  so-called 
brain  of  the  ant  may  perhaps  be  regarded  as  the  most 
wonderful  piece  of  matter  in  the  world. 

That  ants  have  some  power  of  communication  seems  to 
be  proved  by  the  interesting  experiments  of  Sir  John 
Lubbock.  He  found  that  they  could  carry  information  to 
the  nest  of  the  presence  of  larvae,  and  that  the  greater  the 
number  of  larvae  to  be  fetched,  the  greater  the  number  of 
ants  brought  out  to  fetch  them  in  a  given  time.  On  one 
occasion  Sir  John  Lubbock  put  an  ant  to  some  larvae. 
"  She  examined  them  carefully,  and  went  home  without 
taking  one.  At  this  time  no  other  ants  were  out  of  the 
nest.  In  less  than  a  minute  she  came  out  again  with  eight 
friends,  and  the  little  group  made  straight  for  the  heap  of 
larvae.  When  they  had  gone  two-thirds  of  the  way,  I  im- 
prisoned the  marked  ant ;  the  others  hesitated  a  few 
minutes,  and  then,  with  curious  quickness,  returned  home." 
This  is  only  one  observation  out  of  many ;  and  it  shows 
(1)  that  since  the  marked  ant  took  no  larva  home,  she 
must  have  given  information  which  led  the  others  to  come 
out — unless  we  can  suppose  that  the  smell  of  the  larvae 
she  had  examined  still  hung  about  her ;  and  (2)  that  the 
communication  was  not  detailed,  and  probably  was  no 
more  than  "  Come,"  for,  when  the  leader  of  the  party  was 
removed,  the  rest  knew  not  *  where  to  go — very  possibly 
knew  not  why  they  had  been  summoned. 

Passing  now  to  creatures  of  lower  .organization,  it  is 
exceedingly  difficult  so  to  divest  ourselves  of  our  own  special 
mental  garments  as  to  imagine  what  their  simple  and 
rudimentary  constructs  are  like.  Perhaps  we  may  fairly 
surmise  that,  as  visual  olfactory  and  auditory  organs 
develop,  and  differentiate  from  a  common  basis  of  more 
simple  sensation,  the  process  of  outward  projection  has  its 
rudimentary  inception.  The  earthworm,  which  finds  its  way 

*  Professor  Max  Muller  suggests  to  me  that  perhaps  the  ants  were 
frightened. 


Mental  Processes  in  Animals.  359 

to  favourite  food-stuffs  buried  in  the  earth  in  which  it  lives, 
would  seem  to  possess  the  power  of  outward  projection  in 
a  dim  and  possibly  not  very  definite  form.  Through  their 
marginal  bodies — simple  auditory  or  visual  organs — the 
medusae  may  have  a  rudimentary  form  of  this  capacity. 
In  any  case,  they  seem  to  have  the  power  of  localization. 
Mr.  Eomanes  says,*  "A  medusa  being  an  umbrella- shaped 
animal,  in  which  the  whole  of  the  surface  of  the  handle 
and  the  whole  of  the  concave  surface  of  the  umbrella  is 
sensitive  to  all  kinds  of  stimulation,  if  any  point  in  the 
last-named  surface  is  gently  touched  with  a  camel-hair 
brush  or  other  soft  (or  hard)  object,  the  handle  or  manu- 
brium  is  (in  the  case  of  many  species)  immediately  moved 
over  to  that  point,  in  order  to  examine  or  brush  away  the 
foreign  body."  And  the  same  author  thus  describes  t  the 
process  of  discrimination  in  the  sea-anemone :  "  I  have 
observed  that  if  a  sea- anemone  is  placed  in  an  aquarium 
tank,  and  allowed  to  fasten  upon  one  side  of  the  tank  near 
the  surface  of  the  water,  and  if  a  jet  of  sea-water  is  made 
to  play  continuously  and  forcibly  upon  the  anemone  from 
above,  the  result,  of  course,  is  that  the  animal  becomes 
surrounded  by  a  turmoil  of  water  and  air-bubbles.  Yet, 
after  a  short  time,  it  becomes  so  accustomed  to  this  turmoil 
that  it  will  expand  its  tentacles  in  search  of  food,  just  as  it 
does  when  placed  in  calm  water.  If  now  one  of  the  ex- 
panded tentacles  is  gently  touched  with  a  solid  body,  all 
the  others  close  around  that  body  in  just  the  same  way 
as  they  would  were  they  expanded  in  calm  water.  That 
is  to  say,  the  tentacles  are  able  to  discriminate  between 
the  stimulus  which  is  supplied  by  the  turmoil  of  the 
water,  and  that  which  is  supplied  by  their  contact  with 
the  solid  body,  and  they  respond  to  the  latter  stimulus 
notwithstanding  that  it  is  of  incomparably  less  intensity 
than  the  former." 

Here,  in  discrimination,  we  reach  the  lowest  stage  of 
mental  activity.      It  is  exceedingly  difficult,  however,  to 
determine  how  far  such  simple  responses  to  stimuli  are 
*  "  Mental  Evolution  in  Animals,"  p.  82  f  Ibid.  p.  48. 


360  Animal  Life  and  Intelligence. 

merely  organic,  and  how  far  there  enters  a  psychological 
element. 

I  ought  not,  perhaps,  to  pass  over  in  perfect  silence  the 
subject  of  protozoan  psychology.  M.  Binet  has  published 
a  little  book  on  "  The  Psychic  Life  of  Micro-Organisms," 
in  the  preface  of  which  he  says,  "  We  could,  if  it  were 
necessary,  take  every  single  one  of  the  psychical  faculties 
which  M.  Eomanes  reserves  for  animals  more  or  less 
advanced  on  the  zoological  scale,  and  show  that  the  greater 
part  of  these  faculties  belonged  equally  to  micro-organisms." 
He  says  that  "  there  is  not  a  single  infusory  that  cannot 
be  frightened,  and  that  does  not  manifest  its  fear  by  a 
rapid  flight  through  the  liquid  of  the  preparation,"  and  he 
speaks  of  infusoria  fleeing  "  in  all  directions  like  a  flock  of 
frightened  sheep."  He  attributes  memory  to  Folliculina, 
and  instinct  "  of  great  precision  "  to  Difflugia.  He  regards 
some  of  these  animalculse  as  "  endowed  with  memory  and 
volition,"  and  he  describes  the  following  stages : — 
"  1.  The  perception  of  the  external  object. 
"  2.  The  choice  made  between  a  number  of  objects. 
"  3.  The  perception  of  their  position  in  space. 
"  4.  Movements  calculated  either  to  approach  the  body 
and  seize  it  or  to  flee  from  it." 

But  when  we  have  got  thus  far,  we  are  brought  up  by 
the  following  sentence :  "  We  are  not  in  a  position  to 
determine  whether  these  various  acts  are  accompanied  by 
consciousness,  or  whether  they  follow  as  simple  physio- 
logical processes."  Since,  therefore,  the  fear,  memory, 
instinct,  perception,  and  choice,  spoken  of  by  M.  Binet, 
may  be  merely  physiological  processes  (though,  of  course, 
they  may  be  accompanied  by  some  dim  unimaginable  form 
of  consciousness),  it  seems  scarcely  necessary  to  say  more 
about  them  here. 

I  have  now  said  all  that  is  necessary,  and  all  that  I 
think  justified  by  the  modest  scope  of  this  work,  concerning 
the  process  of  construction  in  animals,  and  the  nature  of 
the  constructs  we  may  presume  that  they  form.  The  pro- 


Mental  Processes  in  Animals.  361 

cess  I  hold  to  be  similar  in  kind  throughout  the  animal 
kingdom  wherever  we  may  presume  that  it  occurs  at  all. 
But  the  products  of  the  process  seem  to  me  to  be  pre- 
sumably widely  different.  If  we  steadily  bear  in  mind  the 
fact  that  the  world  of  man  is  a  joint  product  of  an  external 
existence  and  the  human  mind,  and  then  ask  whether  it  is 
conceivable  that  the  joint  products  of  this  external  existence 
and  the  dog-mind,  the  bird-mind,  the  fish-mind,  the  bee- 
mind,  or  the  worm-mind  are  exactly  or  even  closely 
similar,  we  must,  it  seems  to  me,  answer  the  question  with 
an  emphatic  negative. 

We  will  now  consider  the  nature  of  the  inferences  of 
animals.  It  will  be  remembered  that  a  distinction  was 
drawn  between  perceptual  inferences  and  inferences  in- 
volving a  conceptual  element.  As  I  use  the  words,  per- 
ceptual inferences  are  a  matter,  at  most,  of  intelligence ; 
but  conceptual  inferences  involve  the  higher  faculty  of 
reason. 

It  will  be  necessary  here  to  say  somewhat  more  than 
I  have  already  said  concerning  inference.  When  I  see 
an  orange,  that  object  is  mentally  constructed  at  the 
bidding  of  certain  sight-sensations.  All  that  is  actually 
received  is  the  stimulus  of  the  retinal  elements ;  the  rest  is 
suggested  and  supplied  by  the  activity  of  the  mind.  It  is 
sometimes  said  that  this  complementary  part  of  the  per- 
ception is  inferred.  So,  too,  when  I  hear  a  howl  in  the 
street  which  suggests  the  construct  dog,  it  may  be  said 
that  I  infer  the  presence  of  the  dog.  And  again,  when  the 
dog  is  perceived  to  be  in  pain,  it  may  be  said  that  this  is 
an  inference.  Now,  although  the  use  of  the  word  "  infer- 
ence "  to  denote  the  complementary  part  of  a  percept 
seems  a  little  contrary  to  ordinary  usage,  still  there  are 
some  advantages  in  so — with  due  qualification — employing 
it.  But  since,  as  it  seems  to  me,  the  characteristic  of  the 
inference,  if  so  we  style  it,  in  the  formation  of  constructs 
by  immediate  association  is  its  unconscious  nature  (i.e. 
unconscious  as  a  process)  we  may  perhaps  best  meet  the 


362  Animal  Life  and  Intelligence. 

case  by  speaking  of  these  as  unconscious  inferences.  When 
the  inference  is  not  immediate  and  unconscious,  but  in- 
volves a  more  individual  conscious  act  of  the  mind  in  the 
perceptual  sphere,  we  may  speak  of  it  as  intelligent ;  and 
when  the  inference  can  only  be  reached  by  analysis  and  the 
use  of  concepts,  we  may  call  it  rational. 

Denning,  therefore,  "inference"  as  the  passing  of  the 
mind  from  something  immediately  given  to  something  not 
given  but  suggested  through  association  and  experience, 
we  have  thus  three  stages  of  inference  :  (1)  unconscious 
inference  on  immediate  construction  (perceptual)  ;  (2)  in- 
telligent inference,  dealing  with  constructs  and  reconstructs 
(perceptual) ;  and  (3)  rational  inference,  implying  analysis 
and  isolation  (conceptual). 

Concerning  unconscious  inferences  in  animals,  I  need 
add  nothing  to  that  which  I  have  already  said  concerning 
the  process  of  construction.  It  is  concerning  the  intelligent 
inferences  *  of  animals  that  I  have  now  to  speak. 

I  do  not  propose  here  to  bring  forward  a  number  of 
new  observations  on  the  highly  intelligent  actions  which 
animals  are  capable  of  performing.  Mr.  Komanes  has 
given  us  a  most  valuable  collection  of  anecdotes  on  the 
subject  in  his  volume  on  "Animal  Intelligence."  It  is 
more  to  my  purpose  to  discuss  some  of  the  more  remark- 
able of  these,  and  endeavour  to  get  at  the  back  of  them, 
so  as  to  estimate  what  are  the  mental  processes  involved. 
In  doing  so,  the  principle  I  adopt  is  to  assume  that  the 
inferences  are  perceptual,  unless  there  seem  to  be  well- 
observed  facts  which  necessitate  the  analysis  of  the 

*  These  fall  under  the  "  practical  intelligence  "  of  Mr.  Mivart.  All  their 
intelligent  activities,  in  his  view,  are  performed  by  the  exercise  of  merely 
sensitive  faculties,  through  their  "  consentience."  I  agree  to  so  large  an 
extent  with  Mr.  Mivart  in  his  estimate  of  animal  intelligence,  and  in  his 
psychological  treatment,  that  I  the  more  regret  our  wide  divergence  when  we 
come  to  the  philosophy  of  the  subject.  I  am  with  him  in  believing  that 
conception  and  perception,  in  the  sense  he  uses  the  words,  are  beyond  the 
reach  of  the  brute.  But  I  see  no  reason  to  suppose  that  these  higher  faculties 
differ  in  kind  from  the  lower  faculties  possessed  by  animals.  They  differ 
generically,  but  not  in  kind.  I  believe  that,  through  the  aid  of  language, 
the  higher  faculties  have  been  developed  and  evolved  from  the  lower  faculties. 
Here,  therefore,  1  have  to  part  company  from  Mr.  Mivart. 


Mental  Processes  in  Animals.  363 

phenomena,  the  formation  of  isolates,  and  therefore  the 
employment  of  reason  (as  I  have  above  defined  it).  In  doing 
this,  I  shall  seem  to  differ  very  widely  from  Mr.  Eomanes 
and  other  interpreters  of  animal  habits  and  intelligence. 
But  I  believe  that  the  divergence  is  less  wide  than  it 
seems.  I  believe  that  it  is  largely,  but  I  fear  not  entirely, 
a  question  of  the  terms  we  employ. 

Why,  then,  rediscuss  the  question  under  these  new 
terms?  Because  I  believe  that  such  rediscussion  may 
place  the  matter  in  a  fresh  and,  perhaps,  clearer  light. 
The  question  of  the  relation  of  animal  intelligence  to 
human  reason  is  one  upon  which  there  is  a  good  deal  of 
disagreement,  and  one  that  has  been  discussed  and  re- 
discussed.  I  seek  to  put  it  in  a  somewhat  new  light.  I 
have  endeavoured  to  define  carefully  and  accurately  the 
terms  I  use,  and  the  sense  in  which  I  use  them.  I  have 
coined  for  my  own  purposes  unfamiliar  terms  such  as 
"construct,"  "isolate,"  and  "predominant,"  that  I  might 
thereby  be  enabled  to  avoid  the  use  of  terms  which,  from 
the  different  senses  in  which  they  are  employed  by  different 
writers,  have  become  invested  with  a  certain  ambiguity. 
I  trust,  therefore,  that  even  those  with  whom  I  seem  most 
to  disagree  will  allow  that  my  aim  has  not  been  mere 
disputation,  but  scientific  accuracy  and  precision  in  a 
difficult  subject  where  these  qualities  are  of  essential 
importance. 

I  take  first  some  observations  communicated  by  Mr. 
H.  L.  Jenkins  to  Mr.  Eomanes,  since,  though  they  raise  a 
point  which  we  have  already  shortly  considered,  they  form 
a  transition  from  unconscious  to  perceptual  inferences. 
Speaking  of  the  intelligence  of  the  elephant,  Mr.  Jenkins 
says,*  "What  I  particularly  wish  to  observe  is  that  there 
are  good  grounds  for  supposing  that  elephants  possess 
abstract  ideas  ;  for  instance,  I  think  it  is  impossible  to 
doubt  that  they  acquire,  through  their  own  experience, 
notions  of  hardness  and  weight."  He  then  details  obser- 
vations which  show  that  elephants  at  first  hand  up  things 
*  Romanes,  "  Animal  Intelligence,"  p.  401. 


364  Animal  Life  and  Intelligence. 

of  all  kinds  to  their  mahouts  with  considerable  force,  but 
that  after  a  time  the  soft  articles  are  handed  up  rapidly 
and  forcibly  as  before,  but  that  hard  and  heavy  things  are 
handed  up  gently.  "  I  have  purposely,"  he  says,  "  given 
elephants  things  to  lift  which  they  could  never  have  seen 
before,  and  they  were  all  handled  in  such  a  manner  as 
to  convince  me  that  they  recognized  such  qualities  as 
hardness,  sharpness,  and  weight." 

Now,  the  question  I  wish  here  to  ask  is — Do  the 
observations  of  Mr.  Jenkins,  the  nature  of  which  I  have 
indicated,  afford  good  or  sufficient  reasons  for  supposing 
that  these  animals  possess  abstract  ideas  ?  And  I  reply — 
That  depends  upon  what  is  meant  by  abstract  ideas.  If  it 
is  implied  that  the  abstract  ideas  are  isolates;  that  is, 
qualities  considered  quite  apart  from  the  objects  of  which 
they  are  characteristic,  I  think  not.  But  if  Mr.  Jenkins 
means  that  elephants,  in  a  practical  way,  "recognize  such 
qualities  as  hardness,  sharpness,  and  weight "  as  pre- 
dominant elements  in  the  constructs  they  form,  I  am  quite 
ready  to  agree  with  him.  I  much  question,  however, 
whether  there  is  any  conscious  inference  in  the  matter. 
The  elephant  sees  a  new  object,  and  unconsciously  and 
instinctively  builds  the  element  hardness  or  weight  into 
the  construct  that  he  forms.  And  he  shows  his  great 
intelligence  by  dealing  in  an  appropriate  manner  with  the 
object  thus  recognized.  But  I  do  not  think  any  reasoning 
is  required ;  that  is  to  say,  any  process  involving  an 
analysis  of  the  phenomena  with  subsequent  synthesis,  any 
introduction  of  the  conceptual  element. 

Let  us  consider  next  an  observation  which  shows  a 
very  high  degree  of  perceptual  intelligence  on  the  part  of 
the  dog.  Several  observers  have  described  dogs,  which 
had  occasion  to  swim  across  a  stream,  entering  the  water 
at  such  a  point  as  to  allow  for  the  force  of  the  current. 
And  both  Dr.  Eae  and  Mr.  Fothergill  communicated  to  Mr. 
Eomanes  instances  *  of  the  dog's  observing  whether  the 
tide  was  ebbing  or  flowing,  and  acting  accordingly.  Now, 

*  "  Animal  Intelligence,"  p.  465. 


Mental  Processes  in  Animals.  365 

I  believe  that  the  dog  performs  this  action  through  in- 
telligence, and  that  man  explains  it  by  reason.  The  dog 
has  presumably  had  frequent  experience  of  the  effect  of 
the  stream  in  carrying  him  with  it.  He  has  been  carried 
beyond  the  landing-place,  and  had  bother  with  the  mud ; 
but  when  he  has  entered  the  stream  higher  up,  he  has 
nearly,  if  not  quite,  reached  the  landing-stage.  His  keen 
perceptions  come  to  his  aid,  and  he  adjusts  his  action  nicely 
to  effect  his  purpose. 

On  the  bank  sits  a  young  student  watching  him.  He 
sees  in  the  dog's  action  a  problem,  which  he  runs  over 
rapidly  in  his  mind.  Velocity  of  stream,  two  miles  an 
hour.  Width,  -one-eighth  of  a  mile.  Dog  takes  ten 
minutes  to  swim  one-eighth  of  a  mile.  Distance  flowed 
by  the  stream  in  ten  minutes,  one-third  of  a  mile.  Clever 
dog  that !  He  allows  just  about  the  right  distance.  A 
little  short,  though  !  Has  rather  a  struggle  at  the  end. 

The  dog  intelligently  performs  the  feat ;  the  lad  reasons 
it  out. 

I  do  not  know  whether  I  am  making  my  point  suffi- 
ciently clear.  A  wanton  boy  is  constantly  throwing  stones 
at  birds  and  all  sorts  of  objects.  He  does  not  know  much 
about  the  force  of  gravitation  or  the  nature  of  the  curve 
his  stone  marks  out ;  but  he  allows  pretty  accurately  for 
the  fall  of  the  stone  during  its  passage  through  the  air. 
He  acquires  a  catapult ;  and,  being  an  intelligent  lad,  he 
perceives  that  he  must  aim  a  little  above  the  object  he 
wishes  to  hit.  This  is  a  perceptual  inference.  Eeason 
may  subsequently  step  in  and  explain  the  matter,  or  very 
possibly,  being  human,  sparks  of  reason  fly  around  his 
intelligent  action. 

Am  I  using  the  word  "reason"  in  an  unnatural  and 
forced  sense  ?  I  think  not.  My  use  is  in  accord  with  the 
normal  use  of  the  word  by  educated  people.  Two  men  are 
working  in  the  employ  of  a  mechanical  engineer.  Listen 
to  their  employer  as  he  describes  them.  "  A  most  intelligent 
fellow  is  A ;  he  does  everything  by  rule  of  thumb ;  but  he's 
wonderfully  quick  at  perceiving  the  bearing  of  a  new  bit  of 


366  Animal  Life  and  Intelligence. 

work ;  he  sees  the  right  thing  to  do,  though  he  cannot  tell 
you  why  it  should  be  done.  Now,  B  is  a  very  different 
man ;  he  is  slow,  but  he  reasons  everything  out.  A  knows 
the  right  thing  to  do  ;  and  B  can  tell  you  why  it  must  be 
done.  A  has  the  keenest  intelligence,  but  B  the  clearest 
reasoning  faculty.  If  I  have  occasion  to  question  them 
about  any  mechanical  contrivance,  A  says,  '  Let  me  see  it 
work  ; '  but  B  says,  '  Let  me  think  it  out.'  " 

In  other  words,  A,  the  intelligent  man,  deals  with 
phenomena  as  wholes,  and  his  perceptual  inferences  are 
rapid  and  exact ;  while  B,  the  reasoner,  analyzes  the 
phenomena,  and  draws  conceptual  inferences  about  them. 

Let  us  take  next  Dr.  Eae's*  most  interesting  description 
of  the  cunning  of  Arctic  foxes.  These  clever  animals,  he 
tells  us,  soon  learn  to  avoid  the  ordinary  steel  and  wooden 
traps.  The  Hudson  Bay  trappers,  therefore,  set  gun-traps. 
The  bait  is  laid  on  the  snow,  and  connected  with  the 
trigger  of  the  gun  by  a  string  fifteen  or  twenty  feet  long, 
five  or  six  inches  of  slack  being  left  to  allow  for  contraction 
from  moisture.  The  fox,  on  taking  tip  the  bait,  discharges 
the  gun  and  is  shot.  But,  after  one  or  more  foxes  have 
been  shot,  the  cunning  beasts  often  adopt  one  of  two 
devices.  Either  they  gnaw  through  the  string,  and  then 
take  the  bait ;  or  they  tunnel  in  the  snow  at  right  angles 
to  the  line  of  fire,  and  pull  the  bait  downwards,  thus  dis- 
charging the  gun,  but  remaining  uninjured.  This  is 
regarded  by  Dr.  Eae  as  a  wonderful  instance  of  "  abstract 
reasoning." 

Here,  again,  it  is  the  "abstract  reasoning"  that  I 
question.  Do  the  clever  foxes  resemble  the  intelligent 
workman  A,  or  the  abstract  reasoner  B  ?  I  believe  that 
their  actions  are  the  result  of  perceptual  inferences.  They 
adopt  their  cunning  devices  after  one  or  more  foxes  have 
been  shot.  Their  keen  perceptions  (let  me  repeat  that  the 
perceptions  of  wild  animals  are  extraordinarily  keen)  lead 
them  to  see  that  this  food,  quiet  as  it  seems,  has  to  be 
taken  with  caution. 

*  "  Animal  Intelligence,"  p.  430 ;  and  Nature,  vol.  xix.  p.  409. 


Mental  Processes  in  Animals.  367 

With  regard  to  the  devices  adopted,  I  think  we  need 
further  information.  Do  Arctic  foxes  tunnel  in  the  snow 
for  any  other  purposes  ?  What  is  the  proportion  of  those 
who  adopt  this  device  to  those  who  gnaw  through  the 
string  ?  Have  careful  and  reliable  observers  watched  the 
foxes  ?  or  are  their  actions,  as  described  by  Dr.  Kae, 
inferences,  on  the  part  of  the  trappers,  from  the  state  of 
matters  they  found  when  they  came  round  to  examine 
their  traps  ?  Without  fuller  information  on  these  points, 
it  is  undesirable  to  discuss  the  case  further.  Even  if  we 
had  full  details,  however,  we  should  be  as  little  able  to  get 
at  the  process  of  perceptual  inference  in  the  case  of  the  fox 
as  we  are  in  the  case  of  the  intelligent  workman,  who  sees 
the  right  thing  to  do,  but  cannot  tell  you  how  he  reached 
the  conclusion. 

No  one  can  watch  the  actions  of  a  clever  dog  without 
seeing  how  practical  he  is.  He  is  carrying  your  stick  in 
his  mouth,  and  comes  to  a  stile.  A  young  puppy  will  go 
blundering  with  the  stick  against  the  stile,  and,  perhaps, 
go  back  home,  or  get  through  the  bars  and  leave  the  stick 
behind.  But  practical  experience  has  taught  the  clever 
dog  better.  He  lays  down  the  stick,  takes  it  by  one  end, 
and  draws  it  backwards  through  the  opening  at  one  side  of 
the  stile.  A  friend  tells  me  of  a  dog  which  was  carrying  a 
basket  of  eggs.  He  came  to  a  stile  which  he  was  accus- 
tomed to  leap,  poked  his  head  through  the  stile,  deposited 
the  basket,  ran  back  a  few  yards,  took  the  stile  at  a  bound, 
picked  up  the  basket,  and  continued  on  his  course.  "  In- 
telligent fellow  !  "  I  exclaim.  "Yes,"  says  my  friend,  "he 
knew  the  eggs  would  break  if  he  attempted  to  leap  with  the 
basket !  "  This  is  just  the  little  gratuitous,  unwarrantable, 
human  touch  which  is  so  often  filled  in,  no  doubt  in  perfect 
good  faith,  by  the  narrators  of  anecdotes.  Against  such 
interpolations  we  must  be  always  on  our  guard.  It  is 
so  difficult  not  to  introduce  a  little  dose  of  reason. 

Mr.  Eomanes  obtained  from  the  Zoological  Gardens  at 
Eegent's  Park  a  very  intelligent  capuchin  monkey,  on 
which  his  sister  made  a  series  of  most  interesting  and 


368  Animal  Life  and  Intelligence. 

valuable  observations.  This  monkey  on  one  occasion  got 
hold  of  a  hearth-brush,  and  soon  found  the  way  to  unscrew 
the  handle.  After  long  trial,  he  succeeded  in  screwing  it 
in  again,  and  throughout  his  efforts  always  turned  the 
handle  the  right  way  for  screwing.  Having  once  succeeded, 
he  unscrewed  it  and  screwed  it  in  again  several  times  in 
succession,  each  time  with  greater  ease.  A  month  after- 
wards he  unscrewed  the  knob  of  the  fender  and  the  bell- 
handle  beside  the  mantelpiece.  Commenting  on  these 
actions,  Mr.  Romanes  speaks*  of  "the  keen  satisfaction 
which  this  monkey  displayed  when  he  had  succeeded  in 
making  any  little  discovery,  such  as  that  of  the  mechanical 
principle  of  the  screw." 

I  once  watched,  near  the  little  village  of  Ceres,  in  South 
Africa,  a  dung-beetle  trundling  his  dung-ball  over  an 
uneven  surface  of  sand.  The  ball  chanced  to  roll  into  a 
sand  hollow,  from  which  the  beetle  in  vain  attempted  to 
push  it  out.  The  sides  were,  however,  too  steep.  Leaving 
the  ball,  he  butted  down  the  sand  at  one  side  of  the  hollow, 
so  as  to  produce  an  inclined  plane  of  much  less  angle,  up 
which  he  then  without  difficulty  pushed  his  unsavoury 
sphere. 

Now,  it  seems  to  me  that,  if  we  say,  with  Mr.  Eomanes, 
that  the  brown  capuchin  discovered  the  principle  of  the 
screw,  we  must  also  say  that  the  dung-beetle  that  I  observed 
in  South  Africa  was  acquainted  with  the  principle  of  the 
inclined  plane.  Such  an  expression,  I  contend,  involves 
an  unsatisfactory  misuse  of  terms.  A  mechanical  principle 
is  a  concept, f  and  as  such,  in  my  opinion,  beyond  the 
reach  of  the  brute — monkey  or  beetle.  That  of  which  the 
monkey  is  capable  is  the  perceptual  recognition  of  the  fact 
that  certain  actions  performed  in  certain  ways  produce 
certain  results.  Why  they  do  so  he  neither  knows  nor 
cares  to  know.  What  the  brown  capuchin  discovered  was 

*  "  Animal  Intelligence,"  p.  497. 

t  Mr.  Romanes  regards  it  as,  in  the  case  of  the  capuchin,  a  recept.  But 
when  he  speaks  of  a  generic  idea  of  causation,  and  generic  ideas  of  principles, 
and  of  qualities  as  recepts,  I  find  it  exceedingly  difficult  to  follow  him.  They 
seem  to  me  to  be  concepts  supposed  to  be  formed  in  the  absence  of  language. 


Mental  Processes  in  Animals.  369 

not  the  principle  of  the  screw,  but  that  the  action  of  screw- 
ing produced  the  results  he  desired — a  very  different 
matter.  My  friend,  Mr.  S.  H.  Swayne,  tells  me  that  the 
elephant  at  the  Clifton  Zoo,  having  taking  a  tennis-racket 
from  a  boy  who  had  been  plaguing  him,  broke  it  by  leaning 
it  against  a  step  and  deliberately  stepping  on  it  in  the 
middle,  where  it  was  unsupported.  A  most  intelligent 
action.  And  it  would  have  been  a  capital  piece  of  exercise 
for  the  lad's  reasoning  power,  had  he  been  required  to 
analyze  the  matter,  to  show  why  the  elephant's  action  had 
the  desired  effect,  and  set  forth  the  principle  involved.  I 
do  not  think  the  elephant  himself  possesses  the  faculty 
requisite  for  such  a  piece  of  reasoning.  He  is  content 
with  the  practical  success  of  his  actions;  principles  are 
beyond  him. 

I  will  now  give  two  instances  of  intelligence  in  verte- 
brates which  exemplify  phases  of  inference  somewhat 
different  from  those  which  we  have  so  far  considered.  Mr. 
Watson,  in  his  "  Reasoning  Power  of  Animals,"*  tells  of  an 
elephant  which  was  suffering  from  eye-trouble,  and  nearly 
blind.  A  Dr.  Webb  operated  on  one  eye,  the  animal  being 
made  to  lie  down  for  the  purpose.  The  pain  was  intense, 
and  the  great  beast  uttered  a  terrific  roar.  But  the  effect 
was  satisfactory,  for  the  sight  was  partially  restored.  On 
the  following  day  the  elephant  lay  down  of  himself,  and 
submitted  quietly  to  a  similar  operation  on  the  other  eye. 
No  doubt  the  elephant's  action  here  was,  in  part,  the  result 
of  its  wonderful  docility  and  training.  But  there  was  also 
probably  the  inference  that,  since  Dr.  Webb  had  already 
given  him  relief,  he  would  do  so  again.  The  anticipation 
of  relief  outmastered  the  anticipation  of  immediate  dis- 
comfort or  pain.  I  do  not  think,  however,  that  any  one 
is  likely  to  contend  that  any  rational  analysis  of  the 
phenomena  is  necessarily  involved  in  the  elephant's 
behaviour. 

The  other  instance  I  will  quote  was  communicated  by 
Mr.  George  Bidie  to  Nature.]  He  there  gives  an  account 

*  Page  54.  t  Vol.  xx.  p.  96. 

2   B 


370  Animal  Life  and  Intelligence. 

of  a  favourite  cat  which,  during  his  absence,  was  much 
plagued  by  two  boys.  About  a  week  before  his  return  the 
cat  had  kittens,  which  she  hid  from  her  tormentors  behind 
the  book-shelves  in  the  library.  But  when  he  returned 
she  took  them  one  by  one  from  this  retreat,  and  carried 
them  to  the  corner  of  his  dressing-room  where  previous 
litters  had  been  deposited  and  nursed.  Here  abnormal 
circumstances  and  the  reign  of  anarchy  and  persecution 
forced  her  to  adopt  a  hiding-place  where  she  might  bring 
forth  her  young;  but  the  return  of  normal  conditions, 
sovereignty,  and  order  led  her  to  take  up  her  old  quarters 
under  the  protection  of  her  master.  Now,  look  at  the 
description  I  have  given  in  explanation  of  her  conduct. 
See  how  it  bristles  with  conceptual  terms :  "abnormal,"  with 
its  correlative  "normal;"  "anarchy  and  persecution," 
"protection  "  and  "order."  All  this,  I  believe,  is  mine,  and 
not  the  cat's.  For  her  there  was  a  practical  perception, 
in  the  one  case  of  plaguing  boys,  in  the  other  case  of 
protecting  master ;  and  her  action  was  the  direct  outcome 
of  these  perceptions  through  the  employment  of  her  intelli- 
gence. 

Some  stress  fcas  been  laid  on  the  occasional  use  of  tools 
by  animals.  Mr.  Peal*  observed  a  young  elephant  select 
a  bamboo  stake,  and  utilize  it  for  detaching  a  huge 
elephant-leech  which  had  fixed  itself  beneath  the  animal's 
fore  leg  near  the  body.  "Leech-scrapers  are,"  he  says, 
"  used  by  every  elephant  daily."  He  also  saw  an  elephant 
select  and  trim  a  shoot  from  the  jungle,  and  use  it  as  a 
switch  for  flapping  off  flies.  How  far,  we  may  ask,  do 
such  actions  imply  "  a  conscious  knowledge  of  the  relation 
between  the  means  employed  and  the  ends  attained"?! 
That,  again,  depends  upon  how  much  or  how  little  is 
implied  in  this  phrase. 

A  boy  picks  up  a  stone  and  throws  it  at  a  bird ;  he 
comes  home  and  unlocks  the  garden-gate  with  a  key ;  he 
enters  his  room,  and  removes  the  large  "  Liddell  and 

*  Nature,  vol.  xxi.  p.  34. 

t  Komanes,  "  Animal  Intelligence,"  p.  17  :    Definition  of  reason. 


Mental  Processes  in  Animals.  371 

Scott "  which  he  uses  as  a  convenient  object  to  keep  the 
lid  of  his  play-box  shut ;  he  opens  the  box,  and  cuts  him- 
self a  slice  of  cake  with  his  pocket-knife.  Then  he  goes 
to  his  tutor,  who  is  teaching  him  about  means  and  ends, 
and  their  relation  to  each  other.  He  is  told  that  the 
throwing  of  the  stone  was  the  means  by  which  the  death 
of  the  bird,  or  the  end,  was  to  be  accomplished ;  that  the 
use  of  the  knife  was  the  means  by  which  the  end  in  view, 
the  severance  of  a  piece  of  cake,  was  to  be  effected,  and  so 
on.  He  is  led  to  see  that  the  employment  of  a  great  many 
different  things,  differing  in  all  sorts  of  ways — stones,  keys, 
lexicons,  and  knives — may  be  classified  together  as  means  ; 
and  that  a  great  many  various  effects,  the  death  of  a  bird 
or  the  cutting  a  bit  of  cake,  may  be  regarded  as  ends.  He 
is  told  that  when  he  thinks  of  the  means  and  the  ends 
together,  as  means  and  end,  he  will  be  thinking  of  their 
relationship.  And  it  is  explained  to  him  that  means  and 
ends  and  their  relationships  are  concepts,  and  involve  the 
exercise  of  his  reasoning  powers. 

Weary  and  sick  to  death  of  concepts  and  relationships 
and  reason,  at  length  he  escapes  to  the  garden.  Picking 
up  a  light  stick,  he  sweeps  off  the  heads  of  some  peculiarly 
aggravating  poppies,  and  determines  to  think  no  more  of 
means  and  ends,  continuing  to  use  the  stick  meanwhile  as 
a  most  appropriate  means  to  the  end  of  decapitating  the 
poppies.  By  all  which  I  mean  to  imply  that  there  is  a 
great  difference  between  selecting  and  using  a  tool  for  an 
appropriate  purpose,  and  possessing  a  conscious  knowledge 
of  the  relation  between  the  means  employed  and  the  ends 
attained.  I  do  not  think  that  any  conception  of  means, 
or  end,  or  relationship  is  possible  to  the  brute.  But  I 
believe  that  the  elephant  can  perceive  that  this  stick  will 
serve  to  remove  that  leech.  And  if  this  is  what  Mr. 
Eomanes  means  by  its  possessing  a  conscious  knowledge 
of  the  relation  between  the  means  employed  and  the  ends 
attained,  then  I  am,  so  far,  at  one  with  him  in  the  inter- 
pretation of  the  facts,  though  I  disagree  with  his  mode  of 
expressing  them. 


372  Animal  Life  and  Intelligence. 

I  do  not  propose  to  consider  particular  instances  of 
intelligent  inferences  as  displayed  by  the  invertebrates. 
Bees  in  the  manipulation  of  their  comb,  ants  in  the 
economy  of  their  nest,  spiders  in  the  construction  of  their 
web  and  the  use  they  make  of  their  silken  ropes,  show 
powers  of  intelligent  adaptation  which  cannot  fail  to  excite 
our  wonder  and  admiration.  But  apart  from  the  fact  that 
insect  psychology  is  more  largely  conjectural  than  that  of 
the  more  intelligent  mammals,  a  consideration  of  these 
actions  would  only  lead  me  to  reiterate  the  opinion  above 
frequently  expressed.  In  a  word,  I  regard  the  bees  in  their 
cells,  the  ants  in  their  nests,  the  spiders  in  their  webs,  as 
workers  of  keen  perceptions  and  a  high  order  of  practical 
intelligence.  But  I  do  not,  as  at  present  advised,  believe 
that  they  reason  upon  the  phenomena  they  deal  with  so 
cleverly.  Intelligent  they  are ;  but  not  rational. 

Once  more,  let  me  repeat  that  the  sense  in  which  I  use 
the  words  "rational"  and  "reason"  must  be  clearly 
understood  and  steadily  borne  in  mind.  Mr.  Eomanes 
uses  them  in  a  different  sense.  "  Eeason,"  he  says,*  "  is 
the  faculty  which  is  concerned  in  the  intentional  adapta- 
tion of  means  to  ends.  It  therefore  implies  the  conscious 
knowledge  of  the  relation  between  means  employed  and 
ends  attained,  and  may  be  exercised  in  adaptation  to  cir- 
cumstances novel  alike  to  the  experience  of  the  individual 
and  to  that  of  the  species.  In  other  words,  it  implies  the 
power  of  perceiving  analogies  or  ratios,  and  is  in  this  sense 
equivalent  to  the  term  'ratiocination,'  or  the  faculty  of 
deducing  inferences  from  a  perceived  equivalency  of  rela- 
tions. This  latter  is  the  only  sense  of  the  word  that  is 
strictly  legitimate." 

It  is  not  my  intention  to  criticize  this  use  of  the  term 
"  reason."  Whether  animals  are  capable  of  a  conscious 
knowledge  of  the  relation  between  means  employed  and 
ends  attained,  depends,  as  we  have  already  seen,  upon  how 
much  is  implied  by  the  word  "  knowledge  " — whether  the 
knowledge  is  perceptual  or  conceptual.  My  only  care  is 

*  "  Mental  Evolution  in  Animals,"  p.  318. 


Mental  Processes  in  Animals.  373 

to  indicate  what  seem  to  me  the  advantages  of  the  usage 
(legitimate  or  illegitimate)  I  adopt. 

I  repeat,  then,  that  the  introduction  of  the  process  of 
analysis  appears  to  me  to  constitute  a  new  departure  in 
psychological  evolution ;  that  the  process  differs  generically 
from  the  process  of  perceptual  construction  on  which  it  is 
grafted.  And  I  hold  that,  this  being  so,  we  should  mark 
the  departure  in  every  way  that  we  can.  I  mark  it  by  a 
restriction  of  the  word  "intelligence"  to  the  inferences 
formed  in  the  field  of  perception ;  and  the  use  of  the  word 
"  reason  "  when  conceptual  analysis  supervenes.  Whether 
I  am  justified  in  so  doing,  whether  my  usage  is  legitimate 
or  not,  I  must  leave  others  to  decide.  But,  adopting  this 
usage,  I  see  no  grounds  for  believing  that  the  conduct  of 
animals,  wonderfully  intelligent  as  it  is,  is,  in  any  instances 
known  to  me,  rational. 

I  say  that  the  introduction  of  the  process  of  analysis 
appears  to  me  to  constitute  a  new  departure.  This,  how- 
ever, must  not  be  construed  to  involve  any  breach  of 
continuity. 

I  do  not  believe  that  there  is  or  has  been  any  such 
breach  of  continuity.  Take  a  somewhat  analogous  case. 
I  regard  the  introduction  of  aerial  respiration  in  animal 
life  as  a  new  departure.  Organisms  which  had  hitherto 
been  water-breathers  became  air-breathers.  But  I  do  not 
imagine  that  there  was  any  breach  of  continuity  in  respira- 
tion. The  tadpole  begins  life  as  a  water-breather  only ; 
the  frog  into  which  he  develops  is  an  air-breather;  but 
there  is  no  breach  of  continuity  between  the  one  state  and 
the  other.  So,  too,  the  little  child  dwells  in  the  perceptual 
sphere ;  the  man  into  whom  he  develops  is  capable  of 
conceptual  thought;  but  there  is  no  breach  of  continuity 
in  the  mental  life  of  the  child.  It  is  true  that,  with  all 
our  talk  on  the  subject,  we  cannot  say  exactly  when  in  this 
continuous  mental  life  the  new  departure  is  made.  But 
this  is  no  proof  whatever  that  there  is  no  new  departure. 
In  a  sigmoidal  curve  there  is  a  new  departure  where  the 
convex  passes  into  the  concave.  We  may  find  it  difficult 


374  Animal  Life  and  Intelligence. 

to  mark  the  exact  point  of  change.     But  that  does  not  in- 
validate the  fact  that  the  change  does  actually  take  place. 

If  I  be  asked  how,  in  the  course  of  mental  evolution,  the 
new  departure  was  rendered  possible,  I  reply — Through 
language.     The  first  step  was,   I  imagine,  the  naming  of 
predominants.      If  Noire   and    Professor  Max   Miiller  be 
correct  in  their  views,  language  took  its  origin  in  the  asso- 
ciation of  an  uttered  sound  with  certain  human  activities. 
The  action  thus  named  was,  so  to  speak,  floated  off  by  its 
sign.     By  diacritical  marks   attached  to  the  word,  the 
agent,  the  action,  and  the  object  of  the  action  were  distin- 
guished, and  thus  came  to  be  differentiated  the  one  from 
the  other.     Inseparable  in  fact,  they  came  henceforth  to 
be  separable  in  thought.     Here  was  analysis  in  the  germ. 
The  action  or  activity  was  isolated,  and  henceforth  stood 
forth  as  an  element  in  abstract  thought.     All  the  busy 
world  around  was  interpreted  in  terms  of  activities.     The 
host  of  heaven  and  all  the  powers  of  earth  were  named 
according    to   their   predominant    activities.      The   moon 
became  the  measurer,  the  sun  the  shining  one,  the  wind  the 
one  who  bloweth,  the  fire  the  purifier,  and  so  forth.     Our 
verbs  and  nouns,  then,  being  named  predominants  (agents, 
actions,  or  objects),  adjectives   and   adverbs  were   subse- 
quently introduced  to  qualify  these  by  naming  a  quality  less 
predominant,  or  to  indicate  the  how,  the  when,  and  the  where. 
When  once  the  different  activities  and  different  qualities 
came  to  be  named  or  symbolized,  they  were,  as  I  say, 
floated  off  from  the  agents  or  objects,  and  through  isolation 
entered  the  conceptual  sphere.     The  named  predominant 
became  an  isolate.     Body  and  mind  became  separable  in 
thought ;  the  self  was  differentiated  from  the  not-self;  the 
mind  was  turned  inwards  upon  itself  through  the  isolation 
of  its  varying  phases ;   and  the  consciousness  of  the  brute 
became  the  self-consciousness  of  man. 

Language,  and  the  analytical  faculty  it  renders  possible, 
differentiates  man  from  the  brute.  "  If  a  brute,"  says  Mr. 
Mivart,*  "could  think  'is,'  brute  and  man  would  be 

*  "  Lessons  from  Nature,"  pp.  226,  227. 


Mental  Processes  in  Animals.  375 

brothers.  '  Is '  as  the  copula  of  a  judgment  implies  the 
mental  separation  and  recombination  of  two  terms  that 
only  exist  united  in  nature,  and  can,  therefore,  never  have 
impressed  the  sense  except  as  one  thing.  And  '  is,'  con- 
sidered as  a  substantive  verb,  as  in  the  example,  '  This 
man  is/  contains  in  itself  the  application  of  the  copula  of 
judgment  to  the  most  elementary  of  all  abstractions — 
'  thing  '  or  '  something.'  Yet  if  a  being  has  the  power  of 
thinking  'thing'  or  'something,'  it  has  the  power  of 
transcending  space  and  time  by  dividing  or  decomposing 
the  phenomenally  one.  Here  is  the  point  where  instinct 
[intelligence]  ends  and  reason  begins."  I  regard  this  as 
one  of  the  truest  and  most  pregnant  sentences  that  Mr. 
Mivart  has  written. 

And  when  once  the  Logos  had  entered  into  the  mind  of 
man,  and  made  him  man,  it  slowly  but  surely  permeated 
his  whole  mental  being.  Hence  language  is  not  only 
involved  in  our  concepts,  but  also  in  our  percepts,  in  so  far 
as  they  are  ours.  Professor  Max  Miiller  goes  so  far  as  to 
question  whether  an  unnamed  percept  is  possible.  And 
adult  intellectual  man  is  so  permeated  by  the  Logos  that  I 
am  not  prepared  to  disagree  with  him  when  he  says  that 
he  has  no  unnamed  perceptions.  Nevertheless,  the  actions 
of  the  speechless  child  and  our  dumb  companions  show 
that  they  (children  and  animals)  are  capable  of  forming 
mental  products  of  the  perceptual  order.  But  here,  once 
more,  we  must  not  forget  that  it  is  in  terms  of  these  adult 
human  percepts  that  we  interpret  the  percepts  of  children 
and  animals ;  that  in  doing  so  we  cannot  divest  ourselves 
of  the  garment  of  our  conceptual  thought,  that  we  cannot 
banish  the  Logos,  and  that,  therefore,  these  percepts  other 
than  ours  cannot  be  identical  with  ours,  though  they  are  of 
the  same  order,  saving  their  conceptual  element.  We  may 
put  the  matter  thus — 

(1)  x  X  dog-mind      1          Percepts  to  be  interpreted  in  terms  of  (4),  being 

(2)  x  X  cat-mind          =  |     anal  thereto  but  not  identical  therewith. 

(3)  x  X  infant-mind  J 

(4)  x  X  adult    human    mind  =  the    percepts    of    psychologists,    named    or 

namable. 


376  Animal  Life  and  Intelligence. 

If  the  views  that  I  have  thus  very  briefly  sketched  (for 
I  have  no  right  to  offer  an  opinion  on  a  question  of 
linguistic  science)  be  correct,  language  has  made  analysis, 
isolation,  and  conceptual  thought  possible.  But  there  may 
have  been  a  transitory  stage  when  the  word-signs  stood  for 
predominants,  not  yet  for  isolates.  Granting  the  possibility 
or  probability  of  this,  I  am  prepared  to  follow  Professor 
Max  Miiller  in  his  contention  that  language  and  thought, 
from  the  close  of  that  stage  onward,  are  practically  in- 
separable, and  have  advanced  hand-in-hand.  It  is  true 
that  I  can  now  think  out  a  chemical  or  physical  problem 
without  the  use  of  words — the  stages  of  the  experimental 
work  being  visualized,  just  as  a  chess-player  may  think  out 
a  game  in  pictures  of  the  successive  moves.  But,  his- 
torically, I  believe  the  power  to  do  this  has  been  acquired 
through  language  ;  and  if  I  am  able  temporarily  to  isolate 
and  analyze  without  language,  thought  being  at  times  a 
little  ahead  of  naming,  yet  the  fact  remains  that  language 
is  absolutely  necessary  to  make  such  advances  good,  if  not 
for  me,  at  any  rate  for  man. 

And  here  I  would  make  one  more  suggestion.  Professor 
Max  Miiller,  as  the  result  of  analysis  of  the  Aryan  language, 
finds  a  comparatively  small  number  of  roots  which  he  says 
are  in  all  cases  symbolic  of  concepts.  Yes,  for  us  now  they 
symbolize  concepts.  But  in  their  inception  may  they  not 
have  been  symbolic  of  predominants?  Have  we  not  in 
them  the  signs  for  predominants  not  yet  converted  for  the 
primitive  utterers  into  isolates  ?  May  not  these  haye  been 
the  stepping-stones  from  the  perceptual  predominants  of 
animal  man,  to  the  conceptual  isolates  of  rational  man  ? 
Or,  to  modify  the  analogy,  may  they  not  have  been  the 
embryonic  wings  by  which  the  human  race  were  floated  off 
from  the  things  of  sense  into  the  free  but  tenuous  air  of 
abstract  thought  ? 

Lastly,  before  taking  leave  of  the  subject  of  this  chapter, 
I  am  most  anxious  that  it  should  not  be  thought  that,  in 
contending  that  intelligence  is  not  reason,  I  wish  in  any 
way  to  disparage  intelligence.  Nine-tenths  at  least  of  the 


Mental  Processes  in  Animals.  377 

actions  of  average  men  are  intelligent  and  not  rational. 
Do  we  not  all  of  us  know  hundreds  of  practical  men  who 
are  in  the  highest  degree  intelligent,  but  in  whom  the 
rational,  analytic  faculty  is  but  little  developed  ?  Is  it  any 
injustice  to  the  brutes  to  contend  that  their  inferences  are 
of  the  same  order  as  those  of  these  excellent  practical 
folk  ?  In  any  case,  no  such  injustice  is  intended  ;  and  if  I 
deny  them  self-consciousness  and  reason,  I  grant  to  the 
higher  animals  perceptions  of  marvellous  acuteness  and 
intelligent  inferences  of  wonderful  accuracy  and  precision 
— intelligent  inferences  in  some  cases,  no  doubt,  more 
perfect  even  than  those  of  man,  who  is  often  distracted  by 
many  thoughts. 


378  Animal  Life  and  Intelligence. 


CHAPTEE  X. 

THE  FEELINGS   OF  ANIMALS  :    THEIR  APPETENCES  AND  EMOTIONS. 

THERE  is  one  aspect  of  the  mental  processes  of  men  and 
animals  that  we  have  so  far  left  unnoticed — the  aspect  of 
feeling,  the  aspect  of  pleasure  and  pain.  Quite  distinct 
from,  and  yet  intimately  associated  with,  our  perception  of 
a  beautiful  scene,  is  the  pleasure  we  derive  therefrom  ;  and 
quite  distinct  from,  and  yet  inseparably  bound  up  with, 
our  perception  of  a  discordant  clang,  is  the  painful  effect 
that  it  produces. 

We  have,  however,  no  separate  organs  for  the  apprecia- 
tion of  pleasure  and  pain.  These  feelings  arise  out  of,  and 
are  bound  up  with,  our  sensations,  our  perceptions,  and 
especially  with  the  conscious  exercise  of  our  bodily  activities. 
There  may  be,  at  any  rate  in  some  cases,  separate  nerves 
for  the  appreciation  of  the  pleasurable  and  the  painful ; 
but  even  if  this  be  so,  these  shades  of  feeling  are  so  closely 
associated  with  our  other  activities,  mental  and  bodily, 
that  we  may  for  the  present  regard  them  simply  as  the 
accompaniments  of  these  activities. 

The  question  has  been  raised  and  much  discussed 
whether  all  our  activities  are  accompanied  by  some  shade 
or  colouring  of  feeling,  pleasurable  on  the  one  hand,  or 
painful  on  the  other ;  or  whether  some  of  these  activities 
may  not  be  indifferent  in  this  respect,  affording  us  neither 
pleasure  nor  pain.  Put  in  this  way,  I  think  we  may  say 
that  there  may  be  activities  which  are  thus  indifferent. 
But  if  it  be  asked  whether,  in  addition  to  the  pleasurable 
and  painful  feelings,  there  is  a  third  class  of  feelings,  which 
we  may  call  indifferent  or  neutral,  I  am  inclined  to  answer 


Appetence  and  Emotion.  3/9 

it  in  the  negative.  I  hold  that  every  feeling,  as  such,  must 
belong  either  to  the  painful  or  pleasurable  class,  and  that 
if  the  pleasurable  and  painful,  so  to  speak,  exactly  balance 
each  other,  then  feeling,  as  such,  does  not  emerge  into 
consciousness  at  all.  For,  as  Lotze  says,  "  We  apply  the 
name  '  feelings  '  exclusively  to  states  of  pleasure  and  pain, 
in  contrast  with  sensations  as  [the  elements  of]  indifferent 
perceptions  of  a  certain  content." 

The  broadest  division  of  the  feelings  is,  therefore, 
into  pleasurable  on  the  one  hand,  and  painful  on  the 
other. 

Another  general  question  with  regard  to  the  feelings  is — 
With  what  condition  or  state  of  the  bodily  organization  are 
they  associated  ?  In  answer  to  this  question  we  may  say 
(1)  that  any  very  violent  and  abnormal  stimulus  produces 
pain ;  (2)  that  the  conditions  of  pleasure  are  to  be  sought 
within  the  limits  of  the  healthy  and  normal  exercise  of  the 
bodily  functions  and  mental  activities;  (3)  that  within 
these  limits  the  changes  of  activity  consequent  upon  the 
rhythmic  flow  of  normal  organic  processes  bring  with 
them,  in  the  aggregate,  pleasure,  the  delight  of  healthy 
life;  (4)  that  within  these  limits,  again,  we  experience 
pleasure  or  pain,  enjoyment  or  weariness,  ease  or  discom- 
fort, happiness  or  unhappiness,  with  the  continued  rise  and 
fall  of  our  life-tide.  For,  as  Spinoza  says,  "  We  live  in  per- 
petual mutation,  and  are  called  happy  or  unhappy  accord- 
ing as  we  change  for  the  better  or  the  worse."  So  long 
as  our  activities  remain  at  a  dead  level,  there  is  indifference 
— neither  pleasure  nor  pain.  A  rise  of  the  tide  of  activity 
brings  pleasure,  a  fall  the  reverse.  Lastly,  we  may  say 
(5)  that  beyond  the  limits  of  healthy  and  normal  exercise 
there  is,  on  the  one  hand,  excessive  exercise  which,  carried 
far  enough,  may  give  rise,  first  to  fatigue,  and  then  to 
acute  pain;  and,  on  the  other  hand,  deficient  exercise, 
which  may  produce  that  dull  and  numb  form  of  pain  which 
we  call  discomfort,  or  a  sense  of  craving  or  want. 

Pleasures  and  pains  may  thus  be  either  massive  or 
acute,  diffused  or  locally  concentrated.  On  the  whole,  we 


380  Animal  Life  and  Intelligence. 

may  say,  \vith  Mr.  Grant  Allen,*  that  "  the  acute  pains,  as 
a  class,  arise  from  the  action  of  surrounding  destructive 
agencies;  the  massive  pains,  as  a  class,  from  excessive 
function  or  insufficient  nutriment."  But  since  massive 
pains,  when  pushed  to  an  extreme,  merge  into  the  acute 
class,  "  the  two  classes  are  rather  indefinite  in  their  limits, 
being  simply  a  convenient  working  distinction,  not  a 
natural  division."  "Massive  pleasure  can  seldom  or  never 
attain  the  intensity  of  massive  pain,  because  the  organism 
can  be  brought  down  to  almost  any  point  of  innutrition 
or  exhaustion;  but  its  efficient  working  cannot  be  raised 
very  high  above  the  average.  Similarly,  any  special  organ 
or  plexus  of  nerves  can  undergo  any  amount  of  violent 
disruption  or  wasting  away,  giving  rise  to  very  acute  pains ; 
but  organs  are  very  seldom  so  highly  nurtured  and  so  long 
deprived  of  their  appropriate  stimulant  as  to  give  rise  to 
very  acute  pleasure."  The  amount  of  pleasure  varies, 
according  to  Mr.  Grant  Allen,  whose  discussion  of  the 
subject  is,  perhaps,  the  best  and  clearest  we  have,  directly 
as  the  number  of  nerve-fibres  involved,  and  inversely  as 
the  natural  frequency  of  their  excitation.  No  doubt  the 
principles  above  sketched  out  are  somewhat  vague  and 
general ;  but  we  are  scarcely  justified  in  formulating  any 
that  are  more  precise  and  exact. 

Accepting  now  the  theory  of  evolution,  we  may  say, 
furthermore,  that  during  the  long  process  of  the  moulding 
of  life  to  its  environment,  there  has  been  a  constant 
tendency  to  associate  pleasure  with  such  actions  as  con- 
tribute towards  the  preservation  and  conservation  of  the 
individual  and  the  race,  and  to  associate  pain  with  such 
actions  as  tend  to  the  destruction  or  detriment  of  the 
individual  or  the  race.  For  there  can  be  little  doubt  that 
pleasure  and  pain  are  the  primary  incentives  to  action. 
Without  the  association  of  pleasure  with  conservative 
action,  and  pain  with  detrimental  action,  it  is  difficult  to 
conceive  how  the  evolution  of  conscious  creatures  would 
be  possible.  Conservative  action,  if  it  is  to  be  persisted 

*  "  Physiological  ^Esthetics  : "  chapter  on  "  Pleasure  and  Pain." 


Appetence  and  Emotion.  381 

in  by  a  conscious  creature,  must  be  associated  directly  or 
indirectly  with  pleasurable  feelings ;  nay,  more,  if  it  is  to 
be  persistently  persevered  in,  its  non-performance  must  be 
associated  with  that  dull  form  of  pain  which  we  call  a 
craving  or  want.  Only  under  such  conditions  could 
activities  which  tend  to  the  survival  of  the  individual  and 
the  race  be  fostered  and  furthered. 

It  must  be  remembered,  however,  that  such  association 
is  founded  on  experience,  and  has  no  necessary  validity 
beyond  experience.  That  quinine,  though  unpleasant  to 
the  taste,  is,  under  certain  circumstances,  beneficial  to  the 
individual,  and  that  acetate  of  lead,  though  sweet-tasted, 
is  harmful,  cannot  be  fairly  urged  in  opposition  to  this 
principle,  since  the  effects  of  these  drugs  form  no  part  of 
the  normal  experience  of  the  individual  and  the  race.  Nor 
can  it  be  fairly  objected  that  animals  transported  to  new 
countries  often  eat  harmful  and  poisonous  plants  pre- 
sumably because  they  are  nice  ;  for  these  plants  form  part 
of  an  unwonted  environment.  Nor,  again,  is  the  fact  that 
the  association  of  pleasure  with  conservative  action  and 
pain  with  harmful  action  is  not  always  perfect,  in  any 
sense  fatal  to  the  general  principle.  For  the  establishment 
of  the  association  is  still  in  progress  ;  and  with  the  increase 
in  the  complexity  of  life  its  accurate  establishment  is  more 
and  more  difficult.  No  one  is  likely  to  contend  that  what 
appears  to  be  a  general  principle  must  also  be  an  invariable 
rule.  The  general  principle  is  that  under  the  joint  in- 
fluence of  pleasure  (attractive)  and  pain  (repellent)  the 
needle  of  animal  life  sets  towards  the  pole  of  beneficial 
action.  That  the  needle  does  not  always  point  true  only 
illustrates  the  fact  that  life-activities  are  still  imperfect. 

Let  us  notice  that  it  is  under  the  joint  action  of  pleasure 
and  pain  that  the  needle  sets.  We  must  not  think  only 
of  the  positive  aspect,  and  neglect  the  negative.  What  we 
know  as  wants,  cravings,  appetites,  desires,  and  dissatis- 
factions, are  dull  and  continuous  pains,*  which  tend  to 

*  All  of  these,  at  any  rate,  satisfy  Mr.  Herbert  Spencer's  definition. 
Pleasure  he  describes  as  a  feeling  which  we  seek  to  bring  into  consciousness 


382  .  Animal  Life  and  Intelligence. 

drive  us  to  actions  by  which  they  shall  be  annulled,  and 
the  performance  of  which  shall  give  us  the  pleasures  of 
gratification.  Dr.  Martineau  regards  a  felt  want  as  a 
mainspring  of  our  energy.  "  Life,"  he  says,*  "  is  a  cluster 
of  wants,  physical,  intellectual,  affectional,  moral,  each  of 
which  may  have,  and  all  of  which  may  miss,  the  fitting 
object.  Is  the  object  withheld  or  lost  ?  There  is  pain : 
is  it  restored  or  gained?  There  is  pleasure:  does  it 
abide  or  remain  constant?  There  is  content.  The  two 
first  are  cases  of  disturbed  equilibrium,  and  are  so  far 
dynamic  that  they  will  not  rest  till  they  reach  the  third, 
which  is  their  posture  of  stability  and  their  true  end." 
To  this  I  would  only  add  that  the  content  which  follows  on 
the  keen  pleasure  of  satisfaction  is  evanescent,  and  ere 
long  lapses  into  indifference,  on  which  in  due  time  follows 
the  dull  pain  resulting  from  the  recurrent  pressure  of  the 
want  or  desire. 

It  is  clear  that,  in  introducing  these  wants  and  desires, 
we  are  entering  the  sphere  of  the  emotions,  and  it  is  some- 
times said  that  the  emotions  have  their  basis  in  pleasure 
and  pain.  If  by  this  it  is  meant  that  the  emotions  often 
exhibit  more  or  less  prominently  one  or  other  of  these  two 
aspects  of  feeling,  we  may  agree  with  the  statement.  It 
will  be  well,  however,  to  lead  up  to  our  consideration  of 
the  emotions  by  taking  a  general  review  of  the  manner  in 
which  the  organism  responds  to  external  stimuli. 

A  dog  is  lying  dreamily  on  the  lawn  in  the  sunshine. 
Suddenly  he  raises  his  head,  pricks  his  ears,  scents  the 
air,  looks  fixedly  at  the  hedge,  and  utters  a  low  growl. 
Place  your  hand  upon  his  shoulder,  and  you  will  find  that 
his  muscles  are  all  a-tremble.  He  can  restrain  himself  no 
longer,  and  darts  through  the  hedge.  You  follow  him, 
look  over  the  hedge,  and  see  that  it  is  his  old  enemy,  the 
butcher's  cur.  They  are  moving  slowly  past  each  other, 
head  down,  teeth  bared,  back  roughened.  You  whistle 

and  retain  there ;  pain,  as  a  feeling  which  we  seek  to  get  out  of  consciousness 
and  keep  out. 

*  "  Types  of  Ethical  Theory,"  vol.  ii.  p.  350. 


Appetence  and  Emotion.  383 

softly.  Such  a  whistle  would  generally  bring  him  bounding 
to  your  feet.  But  now  it  is  apparently  unheard.  The  two 
dogs  have  a  short  scuffle,  and  the  cur  slinks  off.  Your  dog 
races  after  him  ;  but  after  a  few  minutes  returns,  jumps 
up  at  you  playfully,  and  then  lies  down  again  on  the  grass. 
But  every  now  and  then,  for  ten  minutes  or  so,  he  raises 
his  head  and  growls  softly. 

Let  us  briefly  analyze  the  dog's  actions,  reading  into 
them,  conjecturally,  the  accompaniments  in  consciousness. 
As  he  lies  on  the  lawn,  he  receives  a  sense-stimulus, 
auditory  or  olfactory,  which  gives  rise  to  the  construction 
of  the  percept  dog  (perhaps  particularized  through  olfactory 
discrimination).  About  the  formation  of  constructs  or  per- 
cepts, however,  we  have  already  said  enough ;  we  have 
now  to  consider  their  effects.  The  head  is  raised,  the  ears 
pricked,  and  so  on.  The  dog  is  on  the  alert.  His  attention 
is  roused.  What  are  the  physiological  effects  ?  Certain 
motor-activities  or  tendencies  to  activity.  These  are  of 
two  kinds — first,  in  connection  with  the  sense-organs,  the 
muscles  of  which  are  brought  into  play  in  such  a  way  as 
to  bring  the  organs  to  bear  upon  the  exciting  object ; 
secondly,  in  connection  with  many  other  muscles,  which 
are  innervated,  so  as  to  be  ready  to  act  rapidly  and 
forcibly.  The  first  motor-effect,  that  on  the  muscles  of 
the  sense-organs,  is  a  very  characteristic  physical  con- 
comitant of  the  psychological  state  which  we  term  "  atten- 
tion ; "  the  second  effect,  the  incipient  innervation  of 
muscles  likely  to  be  called  into  play,  is  equally  charac- 
teristic of  the  psychological  state  we  call  alertness. 

Meanwhile  an  emotional  state  is  rising  in  the  mind  of 
the  dog.  We  may  call  it,  conjecturally,  anger  and  com- 
bativeness.  But  what  we  name  it  does  not  much  signify 
for  our  present  purpose.  It  has  a  growing  tendency  to 
work  itself  out  in  a  series  of  definitely  directed  actions. 
And  this  reaches  its  point  of  culmination  when  the  dog 
rushes  through  the  hedge  and  stands  with  bared  teeth 
before  his  antagonist.  A  whole  set  of  appropriate  muscles 
are  now  strongly  innervated.  There  is  probably  a  double 


384  Animal  Life  and  Intelligence. 

innervation — an  innervation  prompting  to  activity  and  an 
innervation  inhibiting  or  restraining  from  activity.  The 
attention  is  so  concentrated  that  he  heeds  not,  probably 
hears  not,  his  master's  whistle.  He  is  keenly  on  the  alert. 
Then  he  sees  his  chance;  the  inhibition  or  restraint  is 
withdrawn,  and  he  flies  at  his  opponent.  The  emotional 
tendency  works  itself  out  in  action.  Even  after  he  has 
resumed  his  place  on  the  lawn,  memories  of  the  emotional 
state  return,  and  lead  him  to  lift  his  head,  slightly  bare 
his  teeth,  and  growl. 

Now,  with  regard  to  the  emotional  state  here  indicated, 
we  may  notice,  first,  that  it  is  initiated  by  a  percept ; 
secondly,  that  associations  of  pleasure  or  pain  are  by  no 
means  the  most  important  or  predominant  characteristics  ; 
thirdly,  that  the  motor-tendencies  seem  to  be  essential,  the 
emotional  state  being  the  psychological  aspect  of  these 
motor -tendencies ;  and,  fourthly,  that  we  should  perhaps  be 
justified  in  speaking  of  a  presentative  emotion  when  the 
percept  which  gives  rise  to  the  emotion  is  presentative  ; 
and  a  representative  emotion  where  the  originating  percept 
is  represented  in  memory.  And  with  regard  to  the  atten- 
tion which  was  incidentally  introduced,  we  may  notice  that 
it,  too,  has  motor-concomitants,  and  that  it  is  directly 
associated  with  the  emotional  state.  If  no  emotional  state 
is  aroused  by  a  percept,  attention  is  not  specially  directed 
to  the  object.  The  concentration  of  the  attention  is  directly 
proportional  to  the  intensity  of  the  emotion  evoked. 

Emotions,  then,  would  seem  from  this  illustration  to  be 
certain  psychological  states  which  accompany  activities  or 
tendencies  to  activity.  They  are  evoked  by  appropriate 
objects  perceived  or  remembered.  Where  the  tendency  is 
towards  the  object,  as  in  the  sexual  emotions,  we  may 
speak  of  it  as  an  appetence;  where  it  is  away  from  the 
object,  as  in  the  emotion  of  fear,  we  may  speak  of  it  as  an 
aversion.  Appetences  are  normally  pleasurable  ;  aversions, 
painful. 

It  is  clear  that  the  organism  must  be  in  a  condition 
fitting  it  to  carry  out  its  various  activities.  And  this  con- 


Appetence  and  Emotion.  385 

dition  is  more  or  less  variable.  In  the  terms  of  our  previous 
analogy  (Chapter  II.)  the  tissues  are  "explosive."  After  a 
series  of  explosions  have  taken  place  in  a  tissue,  its  store 
of  explosive  material  becomes  exhausted,  and  a  powerful 
stimulus  is  required  to  liberate  further  energy  in  the 
exhausted  tissue.  A  period  of  rest  is  required  to  enable 
the  plasmogen  to  generate  a  fresh  store  of  explosive 
material.  As  this  store  increases  to  its  maximum  pitch, 
the  tissue  becomes  more  and  more  ready  to  respond  at  the 
slightest  touch.  Responsiveness  to  external  stimuli  is 
spoken  of  as  sensitiveness;  emotional  responsiveness  is 
called  sensibility.  What  we  have  before  spoken  of  as  a 
want  or  craving  is  a  state  of  heightened  sensibility,  which 
often  gives  rise  to  a  painful  state  of  general  uneasiness. 
It  may  also  give  rise  to  perceptual  representations  in 
memory,  as  may  be  seen  in  the  dreams  experienced  during 
a  state  of  extreme  sexual  sensibility.  If  we  seek  a  basis 
for  the  emotional  states,  therefore,  we  shall  find  it  in 
sensibility  rather  than  in  pleasure  and  pain. 

The  motor-accompaniments  of  the  emotional  states 
have  long  been  known  under  the  title  of  the  "  expression  " 
of  the  emotions.  The  term  is  too  deeply  rooted  to  be 
altered ;  but  we  may  notice  that  what  is  called  the  expres- 
sion of  an  emotion  is  really  its  partial  fulfilment  in  action. 
Some  psychologists,  dissatisfied  with  the  term  "expression 
of  the  emotions,"  as  seeming  to  imply  that  the  emotion  is 
one  thing  and  its  expression  another,  go  so  far  as  to  say 
that  the  motor-accompaniments  are  the  objective  aspect  of 
what,  under  its  subjective  aspect,  is  the  emotion.  It  is 
quite  possible,  however,  to  experience  an  emotion  without 
any  motor-accompaniments  at  all.  Nevertheless,  there  is, 
I  believe,  in  such  cases  an  unfulfilled  tendency  to  action. 

A  most  important  feature  in  general  physiology  and 
psychology  is  the  postponement  or  suppression  of  action.  The 
physiological  faculty  on  which  it  is  based  is  inhibition.  I 
do  not  propose  to  discuss  the  somewhat  conflicting  views 
on  the  physiological  mechanism  of  inhibition.  It  is,  how- 
ever, a  fact  of  far-reaching  importance  which  no  one  is 

2  c 


386  Animal  Life  and  Intelligence. 

likely  to  deny.    In  its  higher  ranges  it  is  the  objective  basis 
and  aspect  of  self-restraint. 

A  stimulus  gives  rise  to  sensation  and  perception ;  the 
perception  gives  origin  to  an  emotional  state;  and  the 
emotional  state  is  fulfilled  in  appropriate  motor-activities. 
The  process  is  a  continuous  one,  and,  in  the  absence  of 
inhibition,  would  in  all  cases  inevitably  fulfil  itself.  But 
through  the  faculty  of  inhibition,  the  final  state  of  activity 
may  be  postponed  or  suppressed.  We  may  place  side  by 
side  the  physiological  series  and  the  accompanying  psycho- 
logical series  thus — 

Stimulus  of     1  .          .  f  Stimulus  of 

>  — > nervous  processes  in  brain— >  < 
sense-organ/  ^  (.      motor-organs. 

Consciousness  of  1  ( Consciousness  of 

sense-stimulus  j^perceptl°n'  emot'°^{     activity. 

The  arrows  pointing  away  from  perception  and  emotion 
are  intended  to  indicate  the  fact  that  the  consciousness  of 
sense-stimulus  on  the  one  hand,  and  of  activity  on  the 
other,  hand,  are  accompaniments  of  the  nervous  processes  in 
the  brain,  and  are  referred  outwards  to  the  sense-organ  or 
the  motor-organ,  as  the  case  may  be.  It  must  be  remem- 
bered that  the  two  series,  physiological  and  psychological, 
belong  to  distinct  phenomenal  orders.  If  one  speaks  of 
emotion  being  fulfilled  in  activity,  and  thus  seems  to  jump 
from  the  psychological  to  the  physiological  series,  one  does 
so  merely  to  avoid  the  appearance  of  pedantry. 

Now,  by  the  postponement  or  suppression  of  action,  the 
process  is  either  arrested  in  its  middle  phase,  the  motor- 
organs  not  being  innervated  at  all,  or,  as  I  believe  to  be 
more  probable,  the  motor-organs  are  doubly  innervated,  a 
stimulus  to  activity  being  counteracted  by  an  inhibitory 
stimulus,  the  two  neutralizing  each  other  either  in  the 
motor-organ  or  the  efferent  nerves  which  convey  the  stimuli. 
In  any  case,  there  is  no  consciousness  *  of  activity.  And 
the  mind  occupies  itself  more  and  more  completely  with 
the  central  processes,  perception,  and  emotion,  and  also,  in 

*  Such  consciousness  of  activity  is  probably  associated  with,  the  innerva- 
tion  of  afferent,  not  efferent,  nerves. 


Appetence  and  Emotion.  387 

human  beings,  conceptual  thoughts  and  emotions.  Never- 
theless, at  any  rate  so  long  as  we  confine  ourselves  to  the 
perceptual  sphere,  these  processes  have  their  normal  fulfil- 
ments in  action,  and,  if  they  become  sufficiently  intense, 
actually  do  so  fulfil  themselves. 

Now,  since  the  emotions  with  which  we  are  now  dealing 
(we  may  call  them  emotions  in  the  perceptual  sphere)  are 
stages  in  the  fulfilment  of  activities  (though  the  activities 
themselves  may  be  suppressed),  it  is  clear  that  there  may 
be  as  many  emotional  states  as  there  are  modes  of  activity. 
Hence,  no  doubt,  the  extreme  difficulty  of  anything  like  a 
satisfactory  classification  of  these  emotions,  especially 
when  the  activities  are  regarded  as  a  merely  extraneous 
expression. 

Moreover,  when  certain  emotions  reach  a  high  pitch  of 
intensity,  they  may  defeat  their  own  object,  and  give  rise,  not 
to  definite  well-executed  motor-activities,  but  to  helpless  con- 
tradictory actions,  affections  of  glandular  and  other  organs, 
and  a  general  condition  of  collapse.  The  emotion  of  fear, 
for  example,  will  lead  to  motor-activities  tending  to  remove 
a  man  from  the  source  of  danger;  but  when  it  reaches 
the  degree  of  dread,  or  its  culmination  terror,  the  effects 
are  markedly  different.  The  countenance  pales,  the  lips 
tremble,  the  pupils  of  the  eyes  become  dilated,  and  there 
is  an  uncomfortable  sensation  about  the  roots  of  the  hair. 
The  bowels  are  often  strongly  affected,  the  heart  palpitates, 
respiration  labours,  the  secretions  of  the  glands  are  de- 
ranged, the  mouth  becomes  dry,  and  a  cold  sweat  bursts 
from  the  skin.  The  muscles  cease  to  obey  the  will,  and  the 
limbs  will  scarcely  support  the  weight  of  the  body.  Here 
we  have  all  the  effects  of  a  prolonged  struggle  to  escape. 
Just  as  such  a  prolonged  struggle  will  at  length  produce 
these  motor  and  other  effects  accompanied  by  the  emotion 
of  terror  ;  so,  if  the  emotion  of  terror  be  produced  directly, 
these  motor  and  other  effects  are  seen  to  accompany  it. 

Mr.  Charles  Eichardson,  the  well-known  engineer  of  the 
Severn  Tunnel,  has  recorded  several  instances  of  railway 
servants  and  others  being  so  affected  by  the  approach  of  a 


388  Animal  Life  and  Intelligence. 

train  or  engine  that  they  have  been  unable  to  save  them- 
selves by  getting  out  of  the  way,  though  there  was  ample 
time  to  do  so.  This  may  have  been  through  the  effect  of 
terror.  But  one  man,  who  was  nearly  killed  in  this  way, 
only  just  saving  himself  in  time,  informed  me  that  he 
experienced  no  feeling  of  terror ;  he  was  unable  to  explain 
why,  but  he  couldn't  help  watching  the  train  as  it  darted 
towards  him.  In  this  case  it  seems  to  have  been  a  sort  of 
hypertrophy  of  attention.  His  attention  was  so  rivetted 
that  he  was  unable  to  make,  or  rather  he  felt  no  desire  to 
make,  the  appropriate  movements.  He  said,  "I  had  to 
shake  myself,  and  only  did  so  just  in  time.  For  in  another 
moment  the  express  would  have  been  on  me.  When  it  had 
passed,  I  came  over  all  a  cold  sweat,  and  felt  as  helpless  as 
a  baby.  I  was  frightened  enough  then."  Cases  of  so-called 
fascination  in  animals  may  be  due  in  some  cases  to  terror, 
but  more  often,  perhaps,  to  a  hypertrophy  of  attention, 
such  as  is  seen  in  the  hypnotic  state.  Speaking  of  the 
effects  of  artificial  light  on  fish,  Mr.  Bateson  says,* 
"  Bass,  pollack,  mullet,  and  bream  generally  get  quickly 
away  at  first,  but  if  they  can  be  induced  to  look  steadily 
at  the  light  with  both  eyes,  they  generally  sink  to  the 
bottom  of  the  tank,  and  on  touching  the  bottom  commonly 
swim  away.  ...  In  the  case  of  mullet,  effects  apparently 
of  a  mesmeric  character  sometimes  occur,  for  a  mullet 
which  has  sunk  to  the  bottom  as  described  will  sometimes 
lie  there  quite  still  for  a  considerable  time.  At  other  times 
it  will  slowly  rise  in  the  water  until  it  floats  with  its  dorsal 
fin  out  of  the  water,  as  though  paralyzed.  .  .  .  When  the 
light  is  first  shown,  turbot  generally  take  no  notice  of  it, 
but  after  about  a  quarter  of  an  hour  I  have  three  times 
seen  a  turbot  swim  up,  and  lie  looking  into  the  lamp 
steadily.  It  seemed  to  be  seized  with  an  irresistible 
impulse  like  that  of  a  moth  to  a  candle,  and  throws  itself 
open-mouthed  at  the  lamp."  As  a  boy  I  used  frequently 
to  "  mesmerize  "  chickens  by  making  them  look  at  a  chalk 

*  Journal  of  Marine  Biological  Association,  New  Series,  vol.  i.  No.  2, 
pp.  216,  217. 


Appetence  and  Emotion.  389 

mark.  They  would  then  lie  for  some  time  perfectly  motion- 
less. Some  such  effect  has,  perhaps,  led  to  the  instinct 
displayed  by  some  animals  of  "  shamming  dead." 

Eeturning  now  to  the  emotions  as  displayed  in  man,  we 
may  take  one  more  example  in  anger.  This  is  an  emotion 
that  arises  from  the  idea  of  evil  having  been  inflicted 
or  threatened.  "  Under  moderate  anger,"  says  Darwin, 
"  the  action  of  the  heart  is  a  little  increased,  the  colour 
heightened,  and  the  eyes  become  bright.  The  respiration 
is  likewise  a  little  hurried  ;  and  as  all  the  muscles  serving 
for  this  purpose  act  in  association,  the  wings  of  the  nostrils 
are  sometimes  raised  to  allow  of  a  free  draught  of  air  ;  and 
this  is  a  highly  characteristic  sign  of  indignation.  The 
mouth  is  commonly  compressed,  and  there  is  almost  always 
a  frown  on  the  brow.  Instead  of  the  frantic  gestures  of 
extreme  rage,  an  indignant  man  unconsciously  throws 
himself  into  an  attitude  ready  for  attacking  or  striking  his 
enemy,  whom  he  will,  perhaps,  scan  from  head  to  foot  in 
defiance.  He  carries  his  head  erect,  with  his  chest  well 
expanded,  and  the  feet  planted  firmly  on  the  ground.  With 
Europeans  the  fists  are  generally  clenched."  "  Under  rage 
the  action  of  the  heart  is  much  accelerated,  or,  it  may  be, 
much  disturbed.  The  face  reddens,  or  it  becomes  purple 
from  the  impeded  return  of  the  blood,  or  may  turn  deadly 
pale.  The  respiration  is  laboured,  the  chest  heaves,  and 
the  dilated  nostrils  quiver.  The  whole  body  often  trembles. 
The  voice  is  affected.  The  teeth  are  clenched  or  ground 
together,  and  the  muscular  system  is  commonly  stimulated 
to  violent,  almost  frantic,  action.  But  the  gestures  of  a 
man  in  this  state  usually  differ  from  the  purposeless 
writhings  and  struggles  of  one  suffering  from  an  agony  of 
pain ;  for  they  represent  more  or  less  plainly  the  act  of 
striking  or  fighting  with  an  enemy." 

These  examples  will  serve  to  remind  the  reader  of  the 
nature  of  those  complex  aggregates  of  organized  feelings 
which  we  call  emotions,  and  will  also  show  the  close 
connection  of  these  emotions  with  the  associated  bodily 
movements  and  activities  which  constitute  their  normal 


3QO  Animal  Life  and  Intelligence. 

fulfilment.  So  close  is  this  connection,  that  the  assumption 
of  the  appropriate  attitude  will  conjure  up  a  faint  revival 
of  the  associated  emotion.  Let  any  one  stand  with  squared 
shoulders,  clenched  fists,  and  set  muscles,  and  he  will  find 
the  respiration  affected,  and  perhaps  also  the  heart-beat, 
and  will  experience  a  faint  revival  of  the  emotion  of  anger. 
Very  different  will  be  his  feelings  as  he  reseats  himself, 
abandons  his  limbs  to  a  posture  of  leisurely  repose,  and 
allows  a  pleasant  smile  to  steal  over  his  features. 

The  next  point  to  notice  about  these  emotions  is  that 
they  are  to  a  large  extent  instinctive,  and  are  evidenced  in 
the  infant  at  so  early  a  period  that  individual  acquisition 
is  out  of  the  question.  In  any  case,  the  basis  of  sensibility 
is  innate.  As  Mr.  Sully  says,*  "  There  are  instinctive 
capacities  of  emotion  of  different  kinds,  answering  to  such 
well-marked  classes  of  feeling  as  fear,  anger,  and  love. 
These  emotions  arise  uniformly  when  the  appropriate  cir- 
cumstances occur,  and  for  the  most  part  very  early  in  life. 
Thus  there  is  an  instinctive  disposition  in  the  child  to  feel 
in  the  particular  way  known  as  anger  or  resentment  when 
he  is  annoyed  or  injured." 

In  this,  as  in  other  cases  of  instinctive  action,  of  which 
we  shall  have  more  to  say  in  the  next  chapter,  it  is,  of 
course,  impossible  to  say  for  certain  how  far  the  activities 
observed  are  associated  writh  psychological  states.  The 
activities  are  undoubtedly  instinctive.  And  their  perform- 
ance by  an  adult  would  be  accompanied  by  an  emotional 
state.  It  is,  therefore,  probable  that  in  the  very  young 
child  they  have  their  emotional  concomitants.  Still,  we 
must  remember  that  oft-repeated  actions  tend  to  become 
automatic,  that  the  accompanying  consciousness  sinks  into 
evanescence,  and  that  it  is,  therefore,  possible  that  the 
emotional  state  may  not  have  that  vividness  which  the 
activities  seem  to  bespeak. 

There  only  remains,  before  passing  on  to  consider  the 
feelings  and  emotions  of  animals,  to  indicate  what  Mr. 
Sully  terms f  "the  three  orders  of  emotion."  The  first 

*  "  Outlines  of  Psychology,"  p.  481.  f  Ibid.  p.  494. 


Appetence  and  Rmotion.  391 

order  comprises  the  individual  and  personal  emotions — 
those  which  are  self-interested  and  have  sole  reference  to 
the  individual  who  feels,  enjoys,  or  suffers.  They  take 
origin  in  percepts,  either  in  presentations  of  sense  or 
representations  in  memory.  The  second  order  introduces 
the  sympathetic  emotions.  They  are  evoked  on  sight  of 
the  sufferings  or  emotional  states  of  others.  If  we  see  a 
woman  insulted,  we  are  filled  with  indignation ;  and  this 
emotion  has  a  sympathetic  origin.  The  third  order  com- 
prises the  complex  feelings  known  as  sentiments.  They 
have  reference  to  certain  qualities  of  objects  or  activities  of 
individuals  which  inspire  admiration  or  disapprobation. 
They  are  abstract  in  their  nature,  and  belong  to  the  con- 
ceptual sphere.  Such  are  love  of  truth,  beauty,  virtue, 
liberty,  justice.  To  become  operative  on  conduct,  however, 
they  need,  at  any  rate  in  the  case  of  mosfc  people,  to  be 
particularized  and  individualized,  or  brought  within  the 
perceptual  sphere,  ere  they  arouse  anything  that  is 
emotional  in  much  more  than  in  name.  As  Dr.  McCosh 
has  well  said,  "No  man  ever  had  his  heart  kindled  by  the 
abstract  idea  of  loveliness,  or  sublimity,  or  moral  excellence, 
or  any  other  abstraction.  That  which  calls  forth  our 
admiration  is  a  lovely  scene ;  that  which  raises  wonder  or 
awe  is  a  grand  scene;  that  which  calls  forth  love  is  not 
loveliness  in  the  abstract,  but  a  lovely  and  loving  person  ; 
that  which  evokes  moral  approbation  is  not  virtue  in  the 
abstract,  but  a  virtuous  agent  performing  a  virtuous  act. 
The  contemplation  of  the  beautiful  and  the  good  cannot 
evoke  deep  or  lively  emotion.  He  who  would  create 
admiration  for  goodness  must  exhibit  a  good  being  per- 
forming a  good  action." 

Turning  now  to  the  lower  animals,  the  first  question 
that  suggests  itself  is — What  are  their  capacities  for 
pleasure  and  pain?  A  very  difficult  question  to  answer. 
We  cannot,  I  think,  hope  to  know  how  much  or  how  little 
the  invertebrates  feel — to  what  degree  they  are  psycho- 
logically sensitive.  Even  among  the  higher  vertebrates  we 


392  Animal  Life  and  Intelligence. 

are  very  apt,  I  imagine,  to  over-estimate  the  intensity  of 
their  feelings.  Among  human-folk  it  is  not  he  who  halloas 
loudest  that  is  necessarily  most  hurt.  And  it  is  only 
through  the  expression  of  their  feelings  in  cries  and  gestures 
that  we  can  conjecture  the  feelings  of  animals.  There  are 
grounds  for  supposing  fcthat  savages  are  far  less  keenly 
sensitive  than  civilized  people.  And  we  have  some  reason 
for  believing  and  hoping  that  our  dumb  companions  are 
less  sensitive  to  pain  than  we  are.  Mr.  G.  A.  Eowell,  for 
example,  in  his  "  Essay  on  the  Beneficent  Distribution  of 
the  Sense  of  Pain,"  tells  us  that  "a  post-horse  came  down 
on  the  road  with  such  violence  that  the  skin  and  sinews  of 
both  the  fore  fetlock  joints  were  so  cut  that,  on  his  getting 
up  again,  the  bones  came  through  the  skin,  and  the  two 
feet  turned  up  at  the  back  of  the  legs,  -the  horse  walking 
upon  the  ends  of  its  leg-bones.  The  horse  was  put  into  a 
field  close  by,  and  the  next  morning  it  was  found  quietly 
feeding  about  the  field,  with  the  feet  and  skin  forced  some 
distance  up  the  leg-bones,  and,  where  it  had  been  walking 
about,  the  holes  made  in  the  ground  by  the  leg-bones  were 
three  or  four  inches  deep."  Mr.  Lament  gives  a  somewhat 
similar  observation  in  the  case  of  the  reindeer.  "  On  one 
occasion,"  he  says,  "  we  broke  one  of  the  fore  feet  of  an 
old  fat  stag  from  an  unseen  ambush ;  his  companions  ran 
away,  and  the  wounded  deer,  after  making  some  attempts 
to  follow  them,  which  the  softness  of  the  ground  and  his 
own  corpulence  prevented  him  doing,  looked  about  him  a 
little,  and  then,  seeing  nothing,  actually  began  to  graze  on 
his  three  remaining  legs,  as  if  nothing  had  happened  of 
sufficient  consequence  to  keep  him  from  his  dinner." 
Colonel  Sir  Charles  W.  Wilson,  in  his  work  "From  Korti 
to  Khartoum,"  gives  similar  instances  with  regard  to 
camels.  "  The  most  curious  thing,"  he  says,*  "  was  that 
they  showed  no  alarm,  and  did  not  seem  to  mind  being  hit. 
One  heard  a  heavy  thud,  and,  looking  round,  saw  a  stream 
of  blood  oozing  out  of  the  wound,  but  the  camel  went  on 
chewing  his  cud  as  if  nothing  at  all  had  happened,  not 

*  Page  70. 


Appetence  and  Emotion.  393 

even  giving  a  slight  wince  to  show  he  was  in  pain."  And, 
again,*  "  I  heard  the  rush  of  the  shot  through  the  air,  and 
then  a  heavy  thud  behind  me.  I  thought  at  first  it  had 
gone  into  the  field-hospital ;  but,  on  looking  round,  found 
it  had  carried  away  the  lower  jaw  of  one  of  the  artillery 
camels,  and  then  buried  itself  in  the  ground.  The  poor 
brute  walked  on  as  if  nothing  had  happened,  and  carried  its 
load  to  the  end  of  the  day." 

With  regard  to  this  question,  then,  of  the  susceptibility 
of  animals  to  pleasure  and  pain,  no  definite  answer  can  be 
given.  That  they  feel  more  or  less  acutely  we  may  be 
sure ;  how  keenly  they  feel  we  cannot  tell ;  but  it  is  better 
to  over-estimate  than  to  under-estimate  their  sensitiveness. 
In  any  case,  whether  their  pain  be  acute  or  dull,  whether 
their  pleasures  be  intense  or  the  reverse,  we  should  do  all 
in  our  power  to  increase  the  pleasures  and  diminish  the 
pains  of  the  dumb  creatures  who  so  meekly  and  willingly 
minister  to  our  wants. 

That  the  bodily  feelings  and  wants  occupy  a  large 
relative  space  in  the  conscious  life  of  brutes  can  scarcely  be 
questioned.  On  the  one  hand  are  the  dull  pains  resulting 
from  the  organic  wants  and  appetences,  and  driving  the 
animal  to  their  gratification;  the  keen  pleasure  that 
accompanies  this  gratification,  when  intelligence  is  so  far 
developed  that  it  can  be  foreseen,  being  a  pull  in  the  same 
direction.  And  on  the  other  hand  are  the  pleasures  of 
the  normal  and  healthy  exercise  of  the  sense-organs  and 
bodily  activities  giving  rise  to  the  pleasures  of  existence, 
the  joys  of  active  and  vigorous  life.  In  the  main,  these 
bodily  feelings,  or  sense-feelings,  as  they  are  sometimes 
called,  seem  to  cluster  round  three  chief  centres — food,  sex, 
and  the  free  exercise  of  the  bodily  activities,  including  in 
some  cases  what  seems  to  be  play.  Give  a  wild  creature 
liberty  and  the  opportunity  of  gratifying  its  appetites ; 
allow  its  bodily  functions  the  alternating  rhythm  of  healthy 
and  vigorous  exercise  and  restorative  repose ;  and  its  life 
is  happy  and  joyous.  It  is  not  troubled  by  the  pressure 

*  Page  104. 


394  Animal  Life  and  Intelligence. 


of  unfulfilled  ideals.  The  very  struggle  for  existence,  keen 
as  it  often  is,  by  calling  into  play  the  full  exercise  of  the 
activities,  ministers  to  the  health  and  happiness  of  brutes 
as  well  as  men.  Sir  W.  E.  Grove  has  preached  *  the 
advantages  of  antagonism.  Speaking  of  the  rabbit,  he 
says,  "  To  keep  itself  healthy,  it  must  exert  itself  for  its 
food;  this,  and  perhaps  avoiding  its  enemies,  gives  it 
exercise  and  care,  brings  all  its  organs  into  use,  and  thus 
it  acquires  its  most  perfect  form  of  life.  An  estate  in 
Somersetshire,  which  I  once  took  temporarily,  was  on  the 
slope  of  the  Mendip  Hills.  The  rabbits  on  one  part  of  it, 
that  on  the  hillside,  were  in  perfect  condition,  not  too  fat 
nor  too  thin,  sleek,  active,  and  vigorous,  and  yielding  to 
their  antagonists,  myself  and  family,  excellent  food.  Those 
in  the  valley,  where  the  pasturage  was  rich  and  luxuriant, 
were  all  diseased,  most  of  them  unfit  for  human  food,  and 
many  lying  dead  on  the  fields.  They  had  not  to  struggle 
for  life  ;  their  short  life  was  miserable  and  their  death 
early;  they  wanted  the  sweet  uses  of  adversity — that  is, 
of  antagonism."  Without  endorsing  the  view  that  these 
rabbits  were  unhealthy  only  because  they  had  too  much 
food  and  comfort — for  the  food,  though  abundant,  may  have 
been  in  some  way  noxious,  and  the  damp  situation  may 
have  been  prejudicial — we  may  still  believe  that  a  struggle 
for  life  is  better  for  animals  (and  men)  than  unlimited  ease 
and  plenty. 

Under  the  influence,  then,  of  these  bodily  pleasures  and 
wants,  the  activities  of  animals  are  drawn  out  and  guided. 
As  Darwin  says,  in  his  autobiography, t  "  An  animal  may 
be  led  to  pursue  that  course  of  action  which  is  most 
beneficial  to  the  species  by  suffering,  such  as  pain,  hunger, 
thirst,  and  fear  ;  or  by  pleasure,  as  in  eating  and  drinking, 
and  in  the  propagation  of  the  species  ;  or  by  both  means 
combined,  as  in  the  search  for  food.  But  pain  or  suffering 
of  any  kind,  if  long  continued,  causes  depression,  and 
lessens  the  power  of  action,  yet  it  is  adapted  to  make  a 
creature  guard  itself  against  any  great  or  sudden  evil. 

*  Kature,  vol.  xxxvii.  p.  619.  t  Vol.  i.  p.  310,  under  date  1876. 


Appetence  and  Emotion.  395 

Pleasurable  sensations,  on  the  other  hand,  may  be  long 
continued  without  any  depressing  effect ;  on  the  contrary, 
they  stimulate  the  whole  system  to  increased  action. 
Hence  it  has  come  to  pass  that  most  or  all  sentient  beings 
have  been  developed  in  such  a  manner,  through  natural 
selection,  that  pleasurable  sensations  serve  as  their  habitual 
guides.  We  see  this  in  the  pleasure  from  exertion,  even 
occasionally  of  great  exertion,  of  the  body  or  mind — in  the 
pleasure  of  our  daily  meals,  and  especially  in  the  pleasure 
derived  from  sociability,  and  from  loving  our  families.  The 
sum  of  such  pleasures  as  these,  which  are  habitual  or 
frequently  recurrent,  give,  as  I  can  hardly  doubt,  to  most 
sentient  beings  an  excess  of  happiness  over  misery,  although 
they  occasionally  suffer  much.  Such  suffering  is  quite 
compatible  with  belief  in  natural  selection ;  which  is  not 
perfect  in  its  action,  but  tends  only  to  render  each  species 
as  successful  as  possible  in  the  battle  for  life  with  other 
species,  in  wonderfully  complex  and  changing  circum- 
stances." 

Passing  now  from  the  bodily  feelings  and  wants  to  the 
emotions,  there  can  be  no  question  that  the  simpler 
emotions,  of  which  I  have  taken  fear  and  anger  as  typical, 
are  shared  with  us  by  the  dumb  brutes.  And  the  interest- 
ing observations  of  Mr.  Douglas  Spalding  showed  beyond 
doubt  that  they  are  instinctive — their  manifestation  being 
prior  to,  and  not  the  outcome  of,  individual  experience. 
Writing  in  Macmillan's  Magazine,  he  says,  "A  young 
turkey,  which  I  had  adopted  when  chirping  within  the 
uncracked  shell,  was,  on  the  morning  of  the  tenth  day  of 
its  life,  eating  a  comfortable  breakfast  from  my  hand,  when 
the  young  hawk  in  a  cupboard  just  beside  us  gave  a  shrill 
'  Chip  !  chip  !  chip  ! '  Like  an  arrow,  the  poor  turkey  shot  to 
the  other  side  of  the  room,  and  stood  there,  motionless  and 
dumb  with  fear,  until  the  hawk  gave  a  second  cry,  when  it 
darted  out  at  the  open  door  right  to  the  extreme  end  of  the 
passage,  and  there,  silent  and  crouched  in  a  corner,  re- 
mained for  ten  minutes.  Several  times  during  the  course 
of  that  day  it  again  heard  these  alarming  sounds,  and  in 


396  Animal  Life  and  Intelligence. 

every  instance  with  similar  manifestations  of  fear."  And 
as  an  example  of  combined  fear  and  anger,  Mr.  Spalding 
says,  "  One  day  last  month,  after  fondling  my  dog,  I  put 
my  hand  into  a  basket  containing  four  blind  kittens  three 
days  old.  The  smell  my  hand  had  carried  with  it  sent 
them  puffing  and  spitting  in  a  most  comical  fashion." 

A  remarkable  instance  of  inherited  antipathy  in  the  dog 
was  communicated  by  Dr.  Huggins  to  Mr.  Darwin.  He 
possessed  an  English  mastiff,  Kepler,  which  was  brought 
when  six  weeks  old  from  the  stable  in  which  he  was  born. 
The  first  time  Dr.  Huggins  took  him  out  he  started  back  in 
alarm  at  the  first  butcher's  shop  he  had  ever  seen,  and 
throughout  his  life  he  manifested  the  strongest  and 
strangest  antipathy  to  butchers  and  all  that  pertained  to 
them.  On  inquiry,  Dr.  Huggins  ascertained  that  in  the 
father,  in  the  grandfather,  and  in  two  half-brothers  of 
Kepler  the  same  curious  antipathy  was  innate.  Of  these, 
Paris,  a  half-brother,  on  one  occasion,  at  Hastings,  sprang 
at  a  gentleman  who  came  into  the  hotel  at  which  his  master 
was  staying.  The  owner  caught  the  dog,  and  apologized, 
saying  he  had  never  known  him  to  behave  thus  before 
except  when  a  butcher  came  into  the  house.  The  gentle- 
man at  once  said  that  was  his  business. 

That  many  animals  display  affection  towards  their 
offspring  and  their  mates,  towards  man  and  towards  other 
companions,  is  a  matter  of  familiar  observation.  Often 
the  attachments  are  strange,  as  of  cats  and  horses,  or 
contrary  to  instinctive  tendencies,  as  between  cats  and 
dogs.  Sometimes  they  are  capricious,  as  when  Mr. 
Romanes's  wounded  widgeon  conceived  a  strong,  persistent, 
and  unremitting  attachment  to  a  peacock ;  *  or  even  insane, 
as  where  a  pigeon  became  the  victim  of  an  infatuation  for 
a  ginger-beer  bottle.  Strong  attachment  to  man  is  often 
exhibited.  Every  one  knows  the  story  which  Mr.  Darwin 
tells  f  of  the  little  monkey  who  bravely  rushed  at  the 
dreaded  baboon  which  had  attacked  his  keeper.  A  friend 

*  "  Mental  Evolution  in  Animals,"  p.  318. 
t  "Descent  of  Man,"  pt.  i.  chap.  iii. 


Appetence  and  Emotion.  397 

of  my  own  (the  Eev.  George  H.  K.  Fisk,  of  Capetown)  tells 
me  the  following  story  (which  may  be  added  to  the  many 
similar  cases  reported  of  dogs)  concerning  a  favourite  cat 
he  had  as  a  boy.  It  happened  that  the  children  of  the 
house,  my  friend  among  the  number,  were  confined  to 
their  room  by  measles.  Their  mother  remained  with  the 
children  by  day  and  night  until  they  were  convalescent. 
She  then  came  down  and  resumed  her  usual  daily  life,  but 
was  shocked  at  the  appearance  of  the  cat,  which  was  little 
more  than  skin  and  bones,  and  would  not  touch  food  or 
milk.  The  cat  seemed  to  know  that  Mrs.  Fisk  could  help 
her,  and  gave  her  no  peace  till  she  had  taken  her  upstairs 
to  the  convalescent  patients.  To  Mrs.  Fisk's  surprise,  the 
cat  snarled  and  beat  the  young  master  with  her  paws. 
Why  the  cat  chose  this  peculiar  method  of  venting  her 
feelings  it  is  difficult  to  say.  But  immediately  afterwards 
she  went  down  into  the  kitchen,  ate  the  meat  and  drank 
the  milk  which  she  had  before  refused  to  touch.  Early 
next  morning  she  mewed  outside  the  young  master's  room  ; 
and,  having  gained  admittance,  sat  at  the  foot  of  the  bed 
until  he  woke,  and  then  licked  his  face  and  hair. 

This  leads  us  on  to  the  class  of  sympathetic  emotions. 
For  the  sympathetic  emotions  are  those  which  centre,  not 
round  the  self,  but  round  some  other  self  in  whose  welfare 
an  interest  is,  in  some  way  and  for  some  reason,  aroused. 
Not  long  ago,  at  the  Hamburg  Zoological  Gardens,  I  saw 
two  baboons  fighting  savagely.  One  at  last  retreated 
vanquished,  with  his  arm  somewhat  deeply  gashed.  He 
climbed  to  a  corner  of  the  cage  and  sat  down,  moodily 
licking  his  wound.  Thither  followed  him  a  little  capuchin, 
and,  though  his  bigger  friend  took  mighty  little  notice  of 
his  overtures,  seemed  anxious  to  comfort  him,  nestling 
against  him,  and  laying  his  head  against  his  side.  So  far 
as  one  could  judge,  it  was  not  curiosity,  but  sympathy, 
that  prompted  his  action. 

The  following  example  of  sympathetic  action  on  the 
part  of  a  dog  towards  a  stranger-dog  is  communicated  to 
me  by  Mrs.  Mann,  a  friend  of  mine  at  the  Cape.  Carlo 


39 8  Animal  Life  and  Intelligence. 

was  a  favourite  black  retriever,  and  a  highly  intelligent 
animal.  "  One  day,"  says  Mrs.  Mann,  "  a  miserable- 
looking  white  dog  came  into  our  yard.  Carlo  went  up  to 
him,  looking  displeased,  dog-fashion,  and  ready  to  fly  at 
the  intruder.  It  was  clear,  however,  that  some  commu- 
nication passed  between  them,  for  Carlo's  wrath  seemed 
disarmed,  and  he  trotted  into  the  kitchen,  coming  out  again 
with  a  chop-bone  (one  with  a  good  deal  of  meat  on  it) 
which  the  cook  had  given  him.  On  looking  into  the  yard, 
the  miserable  cur  was  seen  enjoying  the  bone,  Carlo  sitting 
straight  up  watching  him  with  a  look  of  satisfaction."  * 

That  dogs  feel  sympathy  with  man  will  scarcely  be 
questioned  by  any  one  who  has  known  the  companionship 
of  these  four-footed  friends.  At  times  they  seem  in- 
stinctively to  grasp  our  moods,  to  be  silent  with  us  when 
we  are  busy,  to  lay  their  shaggy  heads  on  our  knees  when 
we  are  worried  or  sad,  and  to  be  quickened  to  fresh  life 
when  we  are  gay  and  glad — so  keen  are  their  perceptions. 
Their  life  with  man  has  implanted  in  them  some  of  the 
needs  of  social  beings  ;  and  as  they  are  ever  ready  to 
sympathize  with  us,  so  do  they  rejoice  in  our  sympathy. 
To  be  deprived  of  that  sympathy,  to  be  neglected,  to  have 
no  attention  bestowed  on  them,  is  to  some  dogs  a  punish- 
ment more  bitter  than  direct  reproof.  Mr. '  Eomanes 
quotes,  t  an  account  given  him  by  Mrs.  E.  Picton  of  a  Skye 
terrier  who  had  the  greatest  aversion  to  being  washed, 
snarling  and  biting  during  the  operation.  Threats,  beating, 
and  starvation  were  all  of  no  avail;  but  the  animal  was 
reduced  to  submission  by  persistent  neglect  on  the  part  of 
his  mistress.  At  the  end  of  a  week  or  ten  days  he  looked 
wretched  and  forlorn,  and  yielded  himself  quite  quietly  and 

*  Miss  Nellie  Maclagan  describes  how  her  Newfoundland  similarly  took 
a  roll  to  a  hungry  pauper-friend  (Nature,  vol.  xxviii.  p.  150).  Mr.  Duncan 
Stewart  gives  (Nature,  vol.  xxviii.  p.  31)  the  case  of  a  cat  who  used  frequently 
to  provide  her  blind  mother  with  food.  Sir  Harry  Lumsden  states  that 
during  the  cold  autumn  of  1878  some  tame  partridges  in  Aberdeenshire 
brought  two  wild  coveys  to  be  fed  near  the  doorstep  of  the  house.  And  a 
case  has  been  communicated  to  me  by  Miss  Agnes  Tanner,  of  Clifton,  of  a 
thrush  that  pulled  up  worms  on  the  lawn  for  a  lame  companion. 

t  "  Animal  Intelligence,"  p.  440. 


Appetence  and  Emotion.  399 

patiently  to  one  of  the  roughest  ablutions  it  had  ever  been 
his  lot  to  experience. 

So  far  I  have  been  content  to  credit  animals  with  very 
general  and  simple  forms  of  emotion — anger,  fear,  antipathy, 
affection,  and  some  form  of  sympathy.  If,  on  the  perusal 
of  familiar  anecdotes,  we  also  credit  them  with  jealousy, 
envy,  emulation,  pride,  resentment,  cruelty,  deceitfulness, 
and  other  more  complex  emotional  states,  we  must  re- 
member that  every  one  of  these,  as  we  know  them,  is 
essentially  human.  It  is  necessary  to  insist  on  the  need 
of  caution  and  the  danger  of  anthropomorphism.  This 
is,  perhaps,  even  more  necessary  in  the  case  of  the  emotions 
than  in  that  of  the  perceptions,  which  we  have  before  con- 
sidered. Even  among  men,  different  individuals  and 
different  races  probably  vary  far  more  in  their  emotions 
than  in  their  perceptions.  The  emotions  of  civilized  man 
have  assumed  their  present  form  in  the  midst  of  complex 
social  surroundings.  They  one  and  all  bear  ineffaceably 
stamped  upon  them  the  human  image  and  superscription. 
In  terms  of  these  complex  human  emotions  we  have  to 
decipher  the  simpler  emotional  states  of  the  lower  animals. 
We  call  them  by  the  same  names ;  we  think  of  them  as 
like  unto  those  that  we  experience.  And  we  can  do  no 
otherwise,  if  we  are  to  consider  them  at  all.  But  let  us 
not  lose  sight  of  the  fact  that  all  we  can  ever  hope  to  see 
in  the  mirror  of  the  animal  mind  is  a  distorted  image  of 
our  own  mental  and  emotional  features.  And  since  the 
mirrors  are  of  varying  and  unknown  curvature,  we  can 
never  hope  to  be  in  a  position  accurately  to  estimate  the 
amount  of  distortion. 

Eemembering  this,  it  is  always  well  to  look  narrowly  at 
every  anecdote  of  animal  intelligence  and  emotion,  and 
endeavour  to  distinguish  observed  fact  from  observer's  inference. 
If  we  take  the  great  number  of  stories  illustrative  of  revenge, 
consciousness  of  guilt,  an  idea  of  caste,  deceitfulness, 
cruelty,  and  so  forth,  in  the  higher  mammalia,  we  shall 
find  but  few  that  do  not  admit  of  a  different  interpretation 
from  that  given  by  the  narrator.  A  cat's  treatment  of  a 


4co  Animal  Life  and  Intelligence. 

mouse  is  adduced  by  a  number  of  witnesses  as  illustrative 
of  cruelty ;  but  others  see  in  this  conduct,  not  cruelty,  but 
practice  and  training  in  an  important  branch  of  the 
business  of  cat-life.  That  is  to  say,  the  act,  though  objec- 
tively cruel  from  the  human  standpoint,  is  not  on  this  view 
performed  from  a  motive  of  cruelty.  Some  time  ago  I 
ventured  to  stroke  the  nose  of  a  little  lion-cub  which  had 
tottered,  kitten-like,  to  the  bars  of  its  cage.  "  I  wish,"  I 
said  shortly  afterwards  to  a  distinguished  animal  painter, 
"  you  could  have  caught  the  look  of  conscious  dignity 
(I  speak  anthropomorphically)  with  which  the  lioness 
turned  and  seemed  to  say,  'How  dare  you  meddle  with 
my  child!'"  "I  have  seen  such  a  look  and  attitude," 
said  Mr.  Nettleship ;  "  but  I  attributed  it,  not  to  pride,  but 
to  fear."  Mr.  Eomanes  quotes,*  as  typically  illustrative  of 
an  "idea  of  caste,"  the  case  of  Mr.  St.  John's  retriever, 
which  struck  up  an  acquaintance  with  a  rat-catcher  and 
his  cur,  but  at  once  cut  his  humble  friends,  and  denied  all 
acquaintanceship  with  them,  on  sight  of  his  master.  I,  on 
the  other  hand,  should  regard  this  case  as  parallel  with 
that  which  I  have  noted  a  hundred  times.  My  dogs  would 
go  out  with  the  nurse  and  children  when  I  was  busy  or 
absent ;  but  if  I  appeared  within  sight,  they  raced  to  me. 
The  stronger  affection  prevailed.  A  dog  is  described^  as 
"  showing  a  deliberate  design  of  deceiving,"  because  he 
hobbled  about  the  room  as  if  lame  and  suffering  from  pain 
in  his  foot.  I  would  suggest  that  there  was  no  pretence, 
no  "deliberate  design  of  deceit,"  in  this  case,  but  a  direct 
association  of  ideas  between  a  hobbling  gait  and  more 
sympathy  and  attention  than  usual.  I  am  not  denying 
objective  deceitfulness  to  the  dog  any  more  than  I  deny 
objective  cruelty  to  the  cat.  My  only  question  is  whether 
the  motive  is  deceit.  We  must  not  forget  that  the  deceitful 
intent  is  a  piece,  not  of  the  observed  fact,  but  of  the 
observer's  inference.  Mr.  Romanes,  for  example,  tells  J  of 
a  black  retriever  who  was  asleep,  or  apparently  asleep,  in 
the  kitchen  of  a  certain  dignitary  of  the  Church.  The 

•  "  Animal  Intelligence,"  p.  442.        f  Ibid.  p.  444.        J  Ibid.  p.  451. 


Appetence  and  Emotion.  401 

cook,  who  had  just  trussed  a  turkey  for  roasting,  was 
suddenly  called  away.  During  her  temporary  absence, 
"the  dog  carried  off  the  turkey  to  the  garden,  deposited  it 
in  a  hollow  tree,  and  at  once  returned  to  resume  his  place 
by  the  fire,  where  he  pretended  to  be  asleep  as  before." 
Unfortunately,  a  perfidious  gardener  had  watched  him, 
and  brought  back  the  turkey,  so  that  the  retriever  did  not 
enjoy  the  feast  he  had  reserved  for  a  quiet  and  undisturbed 
moment.  Assuming  that  the  gardener  and  cook  were 
accurate  in  their  statement  of  fact,  the  deceitful  intent  is 
an  inference  on  their  part,  or  that  of  the  dignitary  of  the 
Church,  or  Mr.  Eomanes.  I  do  not  deny  its  correctness 
from  the  objective  standpoint.  Deceitfulness  is  apparently 
exhibited  by  children  at  a  very  tender  age.  But  for  us 
civilized  adults  deceit  and  its  converse,  truthfulness  in 
action,  mean  something  a  good  deal  more  definite  than 
for  dogs  and  infants. 

Animals  are  often  described  as  harbouring  feelings  of 
revenge  and  vindictiveness.  To  test  this  in  the  elephant, 
Captain  Shipp  gave  an  elephant  a  sandwich  of  cayenne 
pepper.  "He  then  waited,"  says  Mr.  Eomanes,*  "for  six 
weeks  before  again  visiting  the  animal,  when  he  went  into 
the  stable,  and  began  to  fondle  the  elephant  as  he  had 
previously  been  accustomed  to  do.  For  a  time  no  resent- 
ment was  shown,  so  that  the  captain  began  to  think  that 
the  experiment  had  failed ;  but  at  last,  watching  an  oppor- 
tunity, the  elephant  filled  his  trunk  with  dirty  water,  and 
drenched  the  captain  from  head  to  foot."  Here  the  facts 
are  that  an  injury  was  received,  and  that  the  retaliation 
followed  after  an  interval  of  six  weeks.  The  inference 
seems  to  be  that  the  elephant  harboured  feelings  of  revenge 
or  vindictiveness  during  this  period.  It  may  have  been  so. 
It  may  be,  however,  that  the  elephant  never  once  pictured 
the  captain  during  the  six  weeks;  but,  on  s'eeing  him 
again,  remembered  the  injury,  and,  as  we  say,  paid  him  out. 
But  what  we  understand  by  revenge  and  vindictiveness  is 
the  keeping  of  an  injury  before  the  mind  for  the  express 

*  "  Animal  Intelligence,"  p.  387. 

2   D 


4O2  Animal  Life  and  Intelligence. 

purpose  of  ultimately  avenging  it.     And  this  the  elephant, 
to  say  the  least  of  it,  may  not  have  done. 

In  Miss  Eomanes's  interesting  observations  on  the  Cehus 
monkey,  she  says,*  "  He  bit  me  in  several  places  to-day 
when  I  was  taking  him  away  from  my  mother's  bed  after 
his  morning's  game  there.  I  took  no  notice;  but  he 
seemed  ashamed  of  himself  afterwards,  hiding  his  face  in 
his  arms,  and  sitting  quiet  for  a  time."  But,  in  a  footnote, 
we  read,  "  On  subsequent  observation,  I  find  this  quietness 
was  not  due  to  shame  at  having  bitten  me ;  for  whether  he 
succeeds  in  biting  any  person  or  not,  he  always  sits  quiet 
and  dull-looking  after  a  fit  of  passion,  being,  I  think, 
fatigued."  I  quote  this  to  illustrate  the  difference  which  I 
am  endeavouring  to  insist  upon  between  observed  fact  and 
observer's  inference. 

Mr.  Eomanes  comments  f  on  the  remarkable  change 
which  has  been  produced  in  the  domestic  dog  as  com- 
pared with  wild  dogs,  with  reference  to  the  enduring  of 
pain.  "A  wolf  or  a  fox  will  sustain  the  severest  kinds 
of  physical  suffering  without  giving  utterance  to  a  sound, 
while  a  dog  will  scream  when  any  one  accidentally 
treads  upon  its  toes.  This  contrast,"  says  Mr.  Eomanes, 
"is  strikingly  analogous  to  that  which  obtains  between 
savage  and  civilized  man:  the  North  American  Indian, 
and  even  the  Hindoo,  will  endure  without  a  moan  an 
amount  of  physical  pain — or,  at  least,  bodily  injury — 
which  would  produce  vehement  expressions  of  suffering 
from  a  European.  And,  doubtless,  the  explanation  is  in 
both  cases  the  same ;  namely,  that  refinement  of  life  en- 
genders refinement  of  nervous  organization,  which  renders 
nervous  lesions  more  intolerable."  I  cannot  accept  this 
as  the  most  probable  explanation.  In  the  first  place,  the 
human  beings  referred  to  have  different  ideals  in  the  matter 
of  conduct  under  pain  and  suffering.  The  American  Indian 
and  the  Hindoo  have  a  stoic  ideal,  which  does  not  influence 
the  average  European.  On  the  other  hand,  the  dog,  from 
his  association  with  man,  has  learnt  more  and  more  to 

*  "Animal  Intelligence,"  p.  486.  f  Ibid.  p.  141. 


Appetence  and  Emotion.  403 

give  expression  to  his  feelings  in  barks,  whines,  and  yelp- 
ings. To  howl  at  every  little  pain  would  do  a  wolf  no 
good,  but  rather  advertise  him  to  his  enemies ;  to  howl 
when  his  toes  are  trodden  on  makes  most  men  look  where 
they  are  stepping,  and  probably  pet  the  sufferer  for  his 
pains.  In  the  one  case,  to  howl  is  disadvantageous ;  in 
the  other,  it  is  advantageous.  I  do  not,  however,  put 
forward  my  own  explanation  as  necessarily  more  correct 
than  that  given  by  Mr.  Eomanes  (though  I  regard  it  myself 
as  more  probable).  My  object  is  to  show  that  it  is  possible 
for  two  observers  to  regard  the  same  activities  of  animals, 
and  read  into  them  different  psychological  accompaniments. 
Throughout  the  sections  of  Mr.  Eomanes's  work  which  deal 
with  the  emotions,  I  feel  myself  forced  at  almost  every  turn 
to  question  the  validity  of  his  inferences. 

From  all  that  I  have  said  in  the  last  chapter,  it  will  be 
gathered  that  I  am  not  prepared  to  credit  our  dumb  com- 
panions with  a  single  sentiment.  A  sense  of  beauty,  a 
sense  of  the  ludicrous,  a  sense  of  justice,  and  a  sense  of 
right  and  wrong, — these  abstract  emotions  or  sentiments, 
as  such,  are  certainly  impossible  to  the  brute,  if,  as  I  have 
contended,  he  is  incapable  of  isolation  and  analysis.  But, 
as  we  have  already  seen,  even  with  us  these  emotions  have 
to  be  particularized  and  brought  within  the  perceptual 
sphere  ere  they  are  strongly  operative  on  conduct.  We 
are  not  roused  to  indignation  by  an  abstract  sense  of 
injustice,  but  by  the  particular  performance  of  an  unjust 
deed.  Even  so,  however,  the  emotional  state  aroused 
carries  with  it  in  us  some  of  the  spirit  of  the  conceptual 
sphere  from  which  it  has  descended.  The  analogous 
emotions  in  animals  cannot  possess,  if  I  am  right,  any 
tincture  of  this  conceptual  spirit.  And  since  we  cannot 
divest  ourselves  of  our  conceptual  spirituality,  we  cannot 
justly  estimate  what  these  emotional  states,  in  dog  or  ape, 
are  like.  Eemembering  this,  let  us  eee  what  can  be  said 
in  favour  of  a  perceptual  sense  of  injustice,  guilt,  the 
ludicrous,  and  the  beautiful.  In  evidence  of  a  sense  of 
justice,  we  have  the  oft-quoted  case  of  the  turnspit-dog 


404  Animal  Life  and  Intelligence. 

reported  by  Arago  the  astronomer.*  This  dog  refused, 
with  bared  teeth,  to  enter  out  of  his  turn  the  drum  by  the 
revolution  of  which  the  spit  was  rotated.  M.  Arago,  for 
whom  the  pullet  on  the  spit  was  being  dressed,  requested 
that  the  dog's  companion,  after  turning  the  spit  for  a  short 
time,  should  be  released.  Whereupon  the  dog  who  had 
before  been  so  refractory  seemed  satisfied  that  his  turn  for 
drudgery  had  come,  and,  entering  the  wheel  of  his  own 
accord,  began  without  hesitation  to  turn  it  as  usual.  Many 
will  be  prepared  to  maintain  that  dogs  resent  unjust 
chastisement.  A  gentleman  I  met  near  Eio  de  Janeiro 
possessed  a  dog  whose  sensitiveness  was  such  that,  after 
a  reproof,  he  would  leave  the  house,  and  sometimes  not 
return  for  several  days.  His  owner  assured  me  of  his 
belief  that  in  such  cases  the  reproof  had  always  been  un- 
deserved ;  and  he  told  me  of  one  definite  instance  in  which 
the  reproof — never  more  than  verbal — had  been  for  a  theft 
which  was  afterwards  found  to  have  been  committed  by  his 
garden-boy.  On  this  occasion  the  dog  was  away  for  three 
days,  and  returned  in  a  wretched  and  miserable  condition. 
What  shall  we  say  of  such  cases  ?  Seeing  how  complex  is 
what  we  call  a  sense  of  justice,  I  am  not  prepared  to  credit 
the  dog  therewith ;  and  I  am  disposed  to  regard  such 
actions  as  I  have  just  described  as  the  result  of  a  breach 
of  normal  association.  Dogs,  like  men,  are  creatures  of 
habit;  and  breaches  of  normal  association — occurrences 
contrary  to  expectation — give  rise  to  uneasiness,  dissatisfac- 
tion, and  consequent  resentment. 

Conversely,  many  of  the  cases  where  dogs  and  other 
animals  are  said  to  know  when  they  have  done  wrong,  and 
to  suffer  the  pricks  of  conscience,  may  probably  be  satis- 
factorily explained  by  association.  When  my  friend,  coming 
down  into  his  drawing-room,  sees  Tim's  "  guilty  "  look,  he 
suspects  that  the  dog  has,  contrary  to  rule,  been  taking  a 
nap  on  one  of  the  chairs ;  and  his  suspicions  are  not  a 
little  strengthened  by  the  unnatural  warmth  of  the  easiest 
armchair.  "  Ah  !  Tim  always  knows  when  he  has  done 

*  "  Animal  Intelligence,"  p.  443. 


Appetence  and  Emotion.  405 

wrong,"  says  my  friend.  But  not  improbably  the  associa- 
tion in  Tim's  mind  is  a  direct  one  between  a  nap  on  that 
chair  and  his  master's  displeasure.  What  Tim  knows  is, 
perhaps,  not  that  he  has  done  wrong,  but  that  he  will 
"catch  it."  It  is  the  expectation  of  a  reproof,  or  some- 
thing more,  that  gives  rise  to  his  look  of  conscious  guilt. 
In  the  same  way,  the  look  of  "  conscious  rectitude "  we 
often  see  in  some  dogs  may  be  due  to  the  anticipation  of 
a  word  of  commendation.  And,  in  general,  I  fancy  that  the 
association  in  an  animal's  mind  is  between  the  perform- 
ance of  a  given  act  and  the  occurrence  of  certain  con- 
sequences. When  this  association  becomes  definite  it  must, 
I  imagine,  draw  after  it  a  dislike  of  such  actions  as  have 
been  accompanied  by  evil  consequences,  and  a  delight  in 
such  actions  as  have  been  accompanied  by  pleasant  con- 
sequences. And  eventually  this  dislike  or  delight  is  trans- 
ferred from  his  own  actions  to  the  similar  actions  of  others. 
Thus  dogs  punish  their  puppies  for  acts  of  uncleanliness, 
while  cats  are  even  more  particular  in  this  respect.  A 
correspondent  in  Nature  *  gives  a  case  of  a  cat  chastising 
by  a  violent  blow  with  her  paw  her  kitten,  who  was  about 
to  enjoy  a  herring  which  had  been  set  down  before  the 
fire  to  keep  hot.  So,  too,  according  to  Mr.  Darwin,t  "  when 
the  baboons  in  Abyssinia  plunder  a  garden,  they  silently 
follow  their  leader,  and,  if  an  imprudent  young  animal 
makes  a  noise,  he  receives  a  slap  from  the  others  to  teach 
him  silence  and  obedience."  And  Mr.  Schaub  com- 
municated to  Professor  Nipher  }  a  case  of  a  black-and-tan 
terrier  bitch,  whose  pup  had  stolen  a  stocking  from  his 
bedroom,  and  who  followed  the  young  offender,  took  the 
stocking  from  him,  and  returned  it  to  the  owner.  Her 
action  gave  evidence,  he  says,  of  displeasure  at  the  action 
of  the  pup.  And  Mr.  Schaub  contrived  to  have  the  offence 
committed  on  many  successive  mornings,  the  same  per- 
formance being  repeated  each  time. 

*  Mr.  Alexander  Mackennal,  vol.  xxi.  p.  397. 

f  "  Descent  of  Man,"  pt.  i.  chap,  iii.,  quoted  from  Brehm's  "  Thierleben." 

J  Nature,  vol.  xxviii.  p.  32. 


406  Animal  Life  and  Intelligence. 

In  this  connection  I  will  give  two  anecdotes  of  Carlo, 
communicated  to  me  by  Mrs.  Mann.  "  Once  I  came  upon 
Carlo  sitting  in  the  dining-room  doorway,  Dulceline,  the 
cat,  angrily  watching  him  from  the  stairs,  and  also 
evidently  having  an  eye  on  a  leg  of  mutton  half  dragged 
off  the  dish  on  the  dining-table.  Carlo  had  clearly  caught 
the  thief  in  the  act.  He  was  on  guard ;  and  he  seemed 
much  relieved  when  higher  powers  came  on  the  scene. 
Honesty  seemed  part  of  Carlo's  nature.  In  this  matter 
we  never  had  to  give  him  any  lessons.  Nor  could  he  bear 
to  see  dishonesty  in  others.  One  Sunday,  one  of  the  little 
girls  saw  Carlo  coming  along  looking  so  anxiously  at  her 
that  she  knew  he  wanted  her  to  come.  She  therefore 
followed  him,  and  Carlo  took  her  to  the  store-room,  the 
door  of  which  her  sister  had  left  open.  In  the  doorway 
Carlo  stopped,  and  looked  first  up  at  his  mistress  and  then 
into  the  store-room,  as  much  as  to  say,  '  What  can  we 
think  of  this  ?  '  And  truly  there  was  a  certain  little  black- 
and-tan  terrier,  whose  principles  were  by  no  means  of  a 
high  order,  regaling  himself  with  some  cold  meat  that  he 
had  dragged  on  to  the  floor.  Toby  knew  he  was  in  the 
wrong,  and  tried  to  flee.  But  Carlo  stopped  him  as  he 
endeavoured  to  fly  past.  And  when  Toby  was  thereupon 
duly  slapped,  Carlo  sat  straight  up,  with  a  face  of  conscious 
rectitude." 

These  anecdotes,  communicated  to  me  by  a  lady  of 
culture  and  intelligence,  illustrate  how,  in  describing  the 
actions  of  animals,  phraseology  only,  in  strictness,  applic- 
able to  the  psychology  of  man,  is  unwittingly  and  almost 
unavoidably  employed.  Toby's  "principles  were  not  of  a 
high  order,"  yet  he  "  knew  lie  icas  in  the  wrong,"  while  Carlo 
watched  him  receive  his  punishment,  and  "  sat  straight  up, 
with  a  face  of  conscious  rectitude." 

Coming  now  to  a  sense  of  humour  or  a  sense  of  the 
ludicrous,  Darwin  himself  said,*  ''Dogs  show  what  may 
fairly  be  called  a  sense  of  humour,  as  distinguished  from 
mere  play ;  if  a  bit  of  stick  or  other  such  object  be  thrown 

*  "  Descent  of  Mail,"  quoted  by  Romanes,  p.  445. 


Appetence  and  Emotion.  407 

to  one,  he  will  often  carry  it  away  for  a  short  distance  ;  and 
then,  squatting  down  with  it  on  the  ground  close  before 
him,  will  wait  until  his  master  comes  close  to  take  it  away. 
The  dog  will  seize  it  and  rush  away  in  triumph,  repeating 
the  same  manoeuvre,  and  evidently  enjoying  the  practical 
joke."  Mr.  Eomanes  had  a  dog  who  used  to  perform 
certain  self-taught  tricks,  "which  clearly  had  the  object 
of  exciting  laughter.  For  instance,  while  lying  on  his  side 
and  violently  grinning,  he  would  hold  one  leg  in  his  mouth. 
Under  such  circumstances,  nothing  pleased  him  so  much 
as  having  his  joke  duly  appreciated,  while,  if  no  notice  was 
taken  of  him,  he  would  become  sulky."  To  these  I  may 
add  an  observation  of  my  own.  I  used  sometimes,  when 
staying  at  Lancaster  with  a  friend,  to  take  his  dog  Sambo, 
a  highly  intelligent  retriever,  to  the  seashore.  His  chief 
delight  there  was  to  bury  small  crabs  in  the  sand,  and  then 
stand  watching  till  a  leg  or  a  claw  appeared  above  the 
surface,  upon  which  he  would  race  backwards  and  forwards, 
giving  short  barks  of  keen  enjoyment.  This  I  saw  him  do 
on  many  occasions.  He  always  waited  till  a  helpless  leg 
appeared,  and  then  bounded  away  as  if  he  could  not 
contain  the  canine  laughter  that  was  in  him.  Who  shall 
say,  however,  what  was  passing  through  the  mind  of  the 
dog  in  any  of  these  three  cases  ?  The  motive  of  Mr. 
Darwin's  dog  may  have  been  to  prolong  the  game,  though 
I  expect  there  was  something  more  than  this.  Mr.  Romanes's 
dog  exemplified,  perhaps,  the  sense  of  satisfaction  at  being 
noticed.  Sambo's  performance  is  now,  as  it  was  years  ago, 
beyond  me.  But  a  sense  of  humour,  involving  a  delicate 
appreciation  of  the  minor  incongruities  of  life,  is,  I  imagine, 
too  subtle  an  emotion  for  even  Sambo. 

I  pass  now  to  the  sense  of  beauty,  and  I  shall  consider 
this  at  greater  length,  because  of  its  bearing  on  sexual 
selection  and  the  origin  of  floral  beauty. 

The  interesting  experiments  of  Sir  John  Lubbock  already 
alluded  to  seem  to  establish  the  fact  that  bees  have  certain 
colour-preferences.  Blue  and  pink  are  the  most  attractive 
colours ;  yellow  and  red  are  in  less  favour.  No  doubt  these 


408  Animal  Life  and  Intelligence. 

preferences  have  arisen  in  association  with  the  flowers  from 
which  the  bees  obtain  their  nectar.  They  have  a  practical 
basis  of  biological  value.  But  there  seems  no  doubt  that 
certain  colours  are  now  for  them  more  attractive  than 
others.  Bees  and  other  insects  are,  undoubtedly,  attracted 
by  flowers  ;  these  flowers  excite  in  us  an  esthetic  pleasure  ; 
the  bees  are,  therefore,  supposed  to  be  attracted  to  the 
flowers  through  their  possession  of  an  aesthetic  sense. 
Now,  this  does  not  necessarily  follow.  It  is  the  nectar,  not 
the  beauty  of  the  flower,  that  attracts  the  bee.  So  long  as 
the  flower  is  sufficiently  conspicuous  to  be  rapidly  distin- 
guished by  the  insect,  the  conditions  of  the  case  are  met 
so  far  as  insect  psychology  is  concerned.  The  fact  remains, 
however,  that  the  flowers  thus  conspicuous  to  the  insect 
are  fraught  with  beauty  for  us. 

In  the  case  of  sexual  selection  among  birds,  again,  I 
believe  that  the  gorgeous  plumage  has  its  basis  of  origin  in 
that  pre-eminent  vitality  which  Mr.  Tylor  and  Mr.  Wallace 
have  insisted  on.  But,  as  before  indicated,  this  will  not 
serve  to  explain  its  special  character  for  each  several  species 
of  birds.  Here,  again,  conspicuousness  and  recognition 
are  unquestionably  factors.  But  that  the  bright  plumage 
of  male  birds  awakens  emotional  states  in  the  hens,  that  it 
probably  also  arouses  sexual  appetence,  seems  to  be  shown 
by  the  manner  in  which  the  finery  is  displayed  by  the 
male  before  the  female.  I  think  it  is  probable,  also,  that 
pleasure,  becoming  thus  associated  with  bright  colours  in 
the  mate,  is  also  aroused  by  bright  colours  in  other  asso- 
ciations. Thus  the  gardener  bower-bird,  described  by  Dr. 
Beccari,*  collects  in  front  of  its  bower  flowers  and  fruits  of 
bright  and  varied  colours.  It  removes  everything  unsightly, 
and  strews  the  ground  with  moss,  among  which  it  places 
the  bright  objects  from  among  which  the  cock  bird  is  said 
to  select  daily  gifts  for  his  mate's  acceptance  !  Dr.  Gould 
states  that  certain  humming-birds  decorate  their  nests 
"with  the  utmost  taste,"  weaving  into  their  structure 
beautiful  pieces  of  flat  lichen.  If  by  crediting  birds  with 

*  Nature,  vol.  xl.  p.  327. 


Appetence  and  Emotion.  409 

a  sense  of  beauty  we  mean  that  in  them  pleasurable 
emotions  may  be  aroused  on  sight  of  objects  which  we 
regard  as  beautiful,  I  am  not  prepared  to  deny  them  such 
a  sense  of  beauty,  nay,  I  fully  believe  that  such  pleasurable 
feelings  are  aroused  in  them.  When,  however,  it  is  said 
that  the  gorgeous  plumage  of  male  birds  has  been  produced 
by  the  aesthetic  choice  of  their  mates,  I  am  not  so  ready  to 
agree.  A  consciously  aesthetic  motive  has  not,  I  believe, 
been  a  determining  cause.  The  mate  selected  has  been 
that  which  has  excited  the  strongest  sexual  appetence  ;  his 
beauty  has  probably  not,  as  such,  been  distinctly  present 
to  consciousness.  Here,  then,  we  have  again  the  question 
which  arose  in  conection  with  floral  beauty — How  is  it 
that  the  sight  of  the  mates  selected  by  hen  birds  excites  in 
us,  in  so  many  cases,  an  aesthetic  pleasure  ? 

It  is  clear  that  this  is  a  matter  rather  of  human  than 
of  animal  or  comparative  psychology.  As  such,  except  for 
purposes  of  illustration,  it  does  not  fall  within  the  scope  of 
this  work.  I  can,  therefore,  say  but  a  few  words  on  the 
subject.  The  view  that  I  think  erroneous  is  that  either 
floral  beauty  or  the  beauty  of  secondary  sexual  characters 
has  been  produced  on  aesthetic  grounds,  that  is  to  say,  for 
the  sake  of  the  beauty  they  are  seen  by  man  to  possess. 
It  is,  therefore,  to  the  point  to  'draw  attention  to  the  fact 
that  many  of  the  objects  and  scenes  which  excite  in  us  this 
aesthetic  sense  have  certainly  not  been  produced  for  the 
sake  of  their  beauty.  Their  beauty  is  an  adjunct,  a  by- 
product of  rarest  excellence,  but  none  the  less  a  by-product. 

Nothing  can  be  more  beautiful  in  its  way  than  a  well- 
grown  beech  or  lime  tree;  and  yet  it  cannot  be  held  to 
have  been  produced  for  its  beauty's  sake.  The  leaves  of 
many  trees,  shrubs,  and  plants  are  scarcely  less  beautiful 
than  the  flowers.  But  they  cannot  have  been  produced  by 
the  aesthetic  choice  of  insects.  From  the  depth  of  a  mine 
there  may  be  brought  up  a  specimen  of  ruby  copper  ore,  or 
malachite,  or  a  nest  of  quartz  crystals,  or  an  agate,  or  a 
piece  of  veined  serpentine,  which  shall  be  at  once  pro- 
nounced a  delight  to  the  eye.  But  for  the  eye  it  was  not 


4io  Animal  Life  and  Intelligence. 

evolved.  The  grandeur  of  Alpine  scenery,  the  charm  of  a 
winding  river,  the  pleasing  undulations  of  a  flowing  land- 
scape,— no  one  can  say  that  these  were  evolved  for  the 
sake  of  their  beauty.  The  fact  of  their  being  beautiful 
is,  therefore,  no  proof  that  the  blue  gentian,  or  the  red 
admiral,  or  the  robin  redbreast  were  evolved  for  the  sake 
of,  or  by  means  of,  the  beauty  that  they  possess.  Again, 
one  leading  feature  in  the  beauty  of  flowers  is  their 
symmetry.  The  beauty  is,  so  to  speak,  kaleidoscopic 
beauty.  It  is  not  so  much  the  single  veined  or  marbled 
petal  that  is  so  lovely,  as  the  group  of  similar  petals 
symmetrically  arranged.  But  this  symmetry  can  hardly 
be  said  to  have  been  selected  for  its  aesthetic  value;  it  is 
rather  part  of  the  natural  symmetry  of  the  plant.  Even 
with  butterflies  and  birds  and  beasts  the  symmetrical 
element  is  an  important  one  in  their  beauty.* 

I  must  not  attempt  to  analzye  our  sense  of  beauty  or 
endeavour  to  trace  its  origin.  It  appears  to  involve  a 
pleasurable  stimulation  of  the  sense-organs  concerned, 

*  Another  example  of  beauty  which  can  hardly  be  said  to  have  been 
evolved  for  beauty's  sake  is  to  be  seen  in  birds'  eggs.  Mr.  Henry  Seebohm 
regards  the  bright  colours  of  some  birds'  eggs  as  a  difficulty  in  the  way  of  the 
current  interpretation  of  organic  nature.  "  Few  eggs,"  he  says  (Nature,  vol. 
xxxv.  p.  237),  "  are  more  gorgeously  coloured  [than  those  of  the  guillemot], 
and  no  eggs  exhibit  such  a  variety  of  colour.  [They  are  sometimes  of  a  bluish 
green,  marbled  or  blotched  with  full  brown  or  black ;  sometimes  white  streaked 
with  brown ;  sometimes  pale  green  or  almost  white  with  only  the  ghosts  of 
blotches  and  streaks ;  and  sometimes  the  reddish  brown  extends  so  as  to 
form  the  ground-tint  which  is  blotched  with  deeper  brown.]  It  is  impossible 
to  suppose  that  protective  selection  can  have  produced  colours  so  conspicuous 
on  the  white  ledges  of  chalk  cliffs ;  and  sexual  selection  must  have  been 
equally  powerless.  It  would  be  too  ludicrous  a  suggestion  to  suppose  that  a 
cock  guillemot  fell  in  love  with  a  plain- coloured  hen  because  he  remembered 
that  last  season  she  laid  a  gay-coloured  egg." 

If  we  connect  colour  with  metabolic  changes,  its  occurrence  in  association 
with  the  products  of  the  highly  vascular  oviduct  will  not  be  surprising. 
Some  guidance  is,  however,  on  the  principles  advocated  in  Chapter  VL.required 
to  maintain  a  standard  of  coloration.  In  many  cases  such  guidance  is  found 
in  protective  selection,  as  in  the  plover's  eggs  in  our  frontispiece.  In  the 
guillemot's  egg  such  protective  selection  seems  to  be  absent,  aud,  as  Mr. 
Seebohm  himself  says,  "  no  eggs  exhibit  such  a  variety  of  colour." 

In  our  present  connection,  however,  the  point  to  be  noticed  is  that  many 
eggs  are  undoubtedly  beautiful.  But  they  cannot  have  been  in  any  way 
eelected  for  the  sake  of  their  beauty. 


Appetence  and  Emotion.  4 1 1 

together  with  perceptions  of  symmetry,  of  diversity  and 
contrast,  and  of  proportion,  with  a  basis  of  unity.  It  is 
rich  in  suggestions  and  associations.  It  is  heightened  by 
sympathy.  A  beautiful  scene  is  doubly  enjoyable  if  a 
congenial  companion  is  by  our  side. 

"  The  whole  effect  of  a  beautiful  object,  so  far  as  we 
can  explain  it,"  says  Mr.  Sully,*  "is  an  harmonious  con- 
fluence of  these  delights  of  sense,  intellect,  and  emotion,  in 
a  new  combination.  Thus  a  beautiful  natural  object,  as  a 
noble  tree,  delights  us  by  its  gradations  of  light  and  colour, 
the  combination  of  variety  with  symmetry  in  its  contour  or 
form,  the  adaptation  of  part  to  part,  or  the  whole  to  its 
surroundings ;  and,  finally,  by  its  effect  on  the  imagination, 
its  suggestions  of  heroic  persistence,  of  triumph  over  the 
adverse  forces  of  wind  and  storm.  Similarly,  a  beautiful 
painting  delights  the  eye  by  supplying  a  rich  variety  of 
light  and  shade,  of  colour,  and  of  outline;  gratifies  the 
intellect  by  exhibiting  a  certain  plan  of  composition,  the 
setting  forth  of  a  scene  or  incident  with  just  the  fulness  of 
detail  for  agreeable  apprehension  ;  and,  lastly,  touches  the 
many-stringed  instrument  of  emotion  by  an  harmonious 
impression,  the  several  parts  or  objects  being  fitted  to 
strengthen  and  deepen  the  dominant  emotional  effect, 
whether  this  be  grave  or  pathetic  on  the  one  hand,  or 
light  and  gay  on  the  other.  The  effect  of  beauty,  then, 
appears  to  depend  on  a  simultaneous  presentment  in  a 
single  object  of  a  well-harmonized  mass  of  pleasurable 
material  or  pleasurable  stimulus  for  sense,  intellect,  and 
emotion." 

This,  too,  is  what  I  understand  by  an  aesthetic  sense  of 
beauty  ;  and  if  a  hen  bird  has  her  sexual  appetence  evoked 
by  the  bright  display  of  her  mate,  the  emotional  state  she 
experiences  is  something  very  different  from  what  we  know 
as  a  sense  of  beauty.  The  adjective  "  aasthetic  "  should  in 
any  case,  I  think,  be  resolutely  excluded  in  any  discussion 
of  sexual  selection. 

^Esthetics,  like  conceptual  thought,  accompany  the  sup- 

*  "  Outlines  of  Psychology,"  p.  537. 


412  Animal  Life  and  Intelligence. 

pression  or  postponement  of  action.  As  we  have  already 
seen,  the  normal  and  primitive  series  is  (1)  sense -stimulus ; 
(2)  certain  nerve-processes  in  the  brain  which  are  asso- 
ciated with  perception  and  emotion ;  and  (3)  certain  result- 
ing activities.  By  the  suppression  of  action  the  mind 
comes  to  occupy  itself  more  and  more  completely  with  the 
central  processes.  Perception  blossoms  forth  into  con- 
ceptual thought ;  emotion  blossoms  forth  into  aesthetics. 

"  '  Throughout  the  whole  range  of  sensations,  percep- 
tions, and  emotions  which  we  do  not  class  as  aesthetic,'  * 
says  Mr.  Herbert  Spencer,  '  the  states  of  consciousness 
serve  simply  as  aids  and  stimuli  to  guidance  and  action. 
They  are  transitory,  or,  if  they  persist  in  consciousness 
some  time,  they  do  not  monopolize  the  attention ;  that 
which  monopolizes  the  attention  is  something  ulterior,  to 
the  effecting  of  which  they  are  instrumental.  But  in  the 
states  of  mind  we  class  as  aesthetic  the  opposite  attitude 
is  maintained  towards  the  sensations,  perceptions,  and 
emotions.  These  are  no  longer  links  in  the  chain  of  states 
which  prompt  and  guide  conduct.  Instead  of  being  allowed 
to  disappear  with  merely  passing  recognition,  they  are  kept 
in  consciousness  and  dwelt  upon,  their  natures  being  such 
that  their  continued  presence  in  consciousness  is  agree- 
able.' The  action  which  is  the  normal  consequent  on 
sensation  is  here  postponed  or  suppressed;  and  thus  we 
are  enabled  to  make  knowledge  or  beauty  an  end  to  be 
sought  for  its  own  sake  ;  and  thus,  too,  we  are  able  to 
make  progress,  otherwise  impossible,  in  science  and  in  art. 
Sensations  and  perceptions  are  the  roots  from  which  spring 
the  sturdy  trunk  of  action,  the  expanded  leaves  of  know- 
ledge, and  the  fair  blossoms  of  art.  The  leaves  and  the 
flowers  are  the  terminal  products  along  certain  lines  of 
development ;  but  the  function  of  the  leaves  is  to  minister 
to  the  growth  of  the  wood,  and  the  function  of  the  flowers  is 
to  minister  to  the  continuance  and  well-being  of  the  race. 
So,  too,  in  human  affairs.  Knowledge  and  art  are  justified 
by  their  influence  on  conduct ;  truth  and  beauty  must  ever 

*  I  should  add,  "or  as  conceptual  thought." 


Appetence  and  Emotion.  413 

guide  us  towards  right  living ;  and  aesthetics  are  true  or 
false  according  as  they  lead  towards  a  higher  or  a  lower 
standard  of  moral  life."  * 

To  sum  up,  then,  concerning  this  difficult  subject,  the 
following  are  the  propositions  on  which  I  would  lay  stress  : 
(1)  What  we  term  an  aesthetic  sense  of  beauty  involves  a 
number  of  complex  perceptual,  conceptual,  and  emotional 
elements.  (2)  The  fact  that  a  natural  object  excites  in  us 
this  pleasurable  emotion  does  not  carry  with  it  the  implica- 
tion that  the  object  was  evolved  for  the  sake  of  its  beauty. 

(3)  Even  if  we   grant,  as   we   fairly   may,   that   brightly 
coloured  flowers,    in   association  with  nectar,  have   been 
objects  of  appetence  to  insects  ;  and  that  brilliant  plumage, 
in  association  with  sexual  vigour,  has  been  a  factor  in  the 
preferential  mating  of  birds ; — this  is  a  very  different  thing 
from  saying  that,    either  in   the   selection   of  flowers  by 
insects,  or  in  the  selection  of  their  mates  by  birds,  a  con- 
sciously aesthetic  motive   has  been  a  determining  cause. 

(4)  In  fine,  though  animals  may  be  incidentally  attracted 
by  beautiful  objects,  they  have  no  aesthetic  sense  of  beauty. 
A  sense  of  beauty  is  an  abstract  emotion.     Esthetics  in- 
volve ideals  ;  and  to  ideals,  if  what  has  been  urged  in  these 
pages  be  valid,  no  brute  can  aspire. 

What  applies  thus  to  aesthetics  applies  also  to  ethics. 
Few,  however,  will  be  found  to  contend  that  animals  can  be 
moral  or  immoral,  or  have  any  moral  ideas  properly  so  called. 
Mr.  Eomanes  does  indeed  state,  in  the  table  he  prefixes 
to  his  works  on  Mental  Evolution,  that  the  anthropoid 
apes  and  dogs  are  capable  of  "indefinite  morality."  He 
leaves  this  to  be  explained,  however,  in  a  future  work.  In 
the  published  instalment  of  "  Mental  Evolution  in  Man  " 
he  seems  to  contend,!  or,  at  least,  admit,  "  that  the  funda- 
mental concepts  of  morality  are  of  later  origin  than  the 
names  by  which  they  have  been  baptized."  But  he  says 
nothing  of  indefinite  morality,  which  still  remains  for  con- 

*  This  paragraph  is  quoted  from  the  author's  "  Springs  of  Conduct,"  p.  263. 
t  Page  347. 


414  Animal  Life  and  Intelligence. 

sideration  in  another  work.  In  the  mean  while  we  may, 
I  think,  confidently  assume  that  ethics,  like  conceptual 
thought  and  aesthetics,  are  beyond  the  reach  of  the  brute. 
Morality  is  essentially  a  matter  of  ideals,  and  these  belong 
to  the  conceptual  sphere. 

I  have  now  said  enough  *  to  indicate  what  I  mean  by 
advocating  the  exercise  of  extreme  caution  in  our  inferences 
concerning  the  emotional  states  of  animals.  We  must 
remember,  first,  how  liable  to  error  are  our  inferences  in 
these  matters  ;  we  must  remember,  next,  how  complex  and 
essentially  human  are  our  own  emotions.  I  do  not  for  one 
moment  deny  that  in  animals  are  to  be  found  the  perceptual 
germs  of  even  the  higher  emotional  states.  Nevertheless, 
if  we  employ,  in  our  interpretation  of  the  actions  of  animals, 
such  terms  as  "  consciousness  of  guilt,"  "  sense  of  right 
and  wrong,"  "idea  of  justice,"  "  deceitfulness,"  "revenge," 
" vindictiveness,"  "shame,"  and  the  rest,  we  must  not 
forget  that  these  terms  stand  for  human  products,  that  they 
are  saturated  with  conceptual  thought,  and  that  they  must 
be  to  a  large  extent  emptied  of  their  meaning  before  they 
can  become  applicable  to  the  emotional  consciousness  of 
brutes. 

*  I  have  said  nothing  about  the  emotions  of  invertebrates,  because  I  have 
nothing  special  to  say.  They  have,  no  doubt,  emotions  analogous  to  fear, 
anger,  and  so  on.  But  it  is  difficult  to  interpret  their  actions.  The  "  angry  " 
wasp  is,  perhaps,  a  good  deal  more  frightened  than  furious.  Sir  John 
Lubbock's  interesting  experiments  seem  to  show  that  ants  have  what  is 
termed  the  instinct  of  play.  But  this  admirable  observer  has  rendered  it 
probable  that  sympathy  and  affection  in  ants  and  bees  have  been  somewhat 
exaggerated. 


CHAPTEE  XL 
ANIMAL  ACTIVITIES:  HABIT  AND  INSTINCT. 

So  soon  as  one  of  the  higher  animals  comes  into  the  world 
a  number  of  simple  vital  activities  are  already  in  progress 
or  are  at  once  initiated.  Some  of  these  are  what  are 
termed  "  automatic  actions,"  or  actions  which  take  their 
origin  within  the  organ  which  manifests  the  activity; 
such  are  the  heart-beat  and  the  rhythmical  contractions 
of  the  intestines  by  which  the  food  is  pushed  onwards 
through  the  alimentary  canal.  Some  are  reflex,  or 
responsive,  actions,  taking  origin  from  a  stimulus  coming 
from  without ;  such  are  the  contraction  of  the  pupil  of  the 
eye  under  bright  light,  the  pouring  forth  of  the  secretions 
on  the  presence  of  food  in  the  alimentary  canal,  taking  the 
breast,  sneezing,  and  so  forth.  Some  are  partly  automatic 
and  partly  reflex ;  such  is  the  rhythm  of  respiration. 

In  addition  to  these  vital  activities,  there  is  a  vast  body 
of  more  complex  activities,  for  the  performance  of  which 
the  animal  brings  with  it  innate  capacities.  Some  of 
these,  which  we  term  "instinctive,"  are  performed  at  once 
and  without  any  individual  training,  as  when  a  chicken  steps 
out  into  the  world,  runs  about,  and  picks  up  food  without 
learning  or  practice.  Others,  which  we  term  "habitual," 
are  more  or  less  rapidly  learnt,  and  are  then  performed 
without  forethought  or  attention.  The  store  of  innate 
capacity  is  often  very  large ;  and  a  multitude  of  activities 
are  ere  long  performed  with  ease  and  certainty  so  soon  as 
the  animal  has  learnt  to  use  the  organization  it  thus 
inherits.  And  lastly,  built  upon  this  as  a  basis,  by  recom- 
biiiing  of  old  activities  in  new  modes,  and  by  special  applica- 


4i 6  Animal  Life  and  Intelligence. 

tion  of  the  activities  to  special  circumstances,  we  have  the 
activities  which  we  term  "  intelligent ;  "  and  here  again  the 
activities  are  sometimes  divided  into  two  classes,  answering 
respectively  to  the  reflex  and  the  automatic,  but  on  a 
higher  plane,  according  as  they  are  responsive  to  stimuli 
coming  more  or  less  directly  from  without,  or  spontaneous 
and  taking  their  origin  from  within.  But  it  is  probably 
rather  the  remoteness  and  indirectness  of  the  responsive 
element  than  its  absence  that  characterizes  these  spon- 
taneous activities. 

Another  classification  of  activities  is  into  voluntary  and 
involuntary.  Voluntary  actions  are  consciously  performed 
for  the  attainment  of  some  more  or  less  definite  end  or 
object.  Involuntary  actions,  though  they  may  be  accom- 
panied by  consciousness,  and  though  they  may  be  apparently 
purposive,  are  performed  without  intention.  Notwith- 
standing the  conscious  element,  they  may,  perhaps,  be 
regarded  as  rather  physiological  than  psychological.  The 
simple  vital  activities  belong  to  this  class.  But  some  are 
much  more  complex.  If,  when  I  am  watching  the  cobra  at 
the  Zoo,  it  suddenly  strikes  at  the  glass  near  my  face,  I 
involuntarily  start  back.  The  action  is  apparently  pur- 
posive, that  is  to  say,  an  observer  of  the  action  would 
perceive  that  it  was  performed  for  a  definite  end,  the 
removal  from  danger ;  it  is  also  accompanied  by  conscious- 
ness ;  but  it  is  unintentional,  no  representation  of  the  end 
to  be  gained  or  the  action  to  be  performed  being  at  the 
moment  of  action  framed  by  the  mind.  On  the  other 
hand,  if  I  perform  a  voluntary  act,  such  as  selecting  and 
lighting  a  cigar,  there  is  first  a  desire  or  motive  directed 
to  a  certain  end  in  view,  involving  an  ill-defined  representa- 
tion of  the  means  by  which  that  end  may  be  achieved ; 
and  this  is  followed  by  the  fulfilment  of  the  desire  through 
the  application  of  the  means  to  the  performance  of  the  act. 

In  the  carrying  out  of  voluntary  activities,  then,  both 
perception  and  emotional  appetence  are  involved.  There 
are  construction  and  reconstruction,  memory  and  antici- 
pation, and  interwoven  therewith  the  motive  elements  of 


Habit  and  Instinct.  4 1 7 

appetence  or  aversion.  It  is  emotion  that  gives  force  and 
power  to  the  motive.  And  this  must  be  regarded  as  the 
dynamic  element  in  voluntary  activity,  while  intelligence 
is  the  directive  element.  Feeling  is  the  horse  in  the 
carriage  of  life,  and  Intelligence  the  coachman. 

Let  us  here  note  that,  in  speaking  of  the  activities  of 
animals  and  the  motives  by  which  they  are  prompted,  we 
are  forced,  if  we  would  avoid  pedantry,  to  leap  backwards 
and  forwards  across  the  chasm  which  separates  the  mental 
from  the  physical.  Motives,  as  we  know  them,  are  mental 
phenomena;  the  activities,  as  we  see  them,  are  physical 
phenomena.  The  two  sets  of  phenomena  belong  to  distinct 
phenomenal  categories.  In  ordinary  speech,  when  we  pass 
and  repass  from  motives  to  actions,  and  from  actions  to 
the  feelings  they  may  give  rise  to,  we  are  apt  to  be  forgetful 
of  the  depth  of  the  chasm  we  so  lightly  leap.  And  this  is 
no  doubt  because  the,  chasm,  though  so  infinitely  deep,  is 
so  infinitely  narrow.  There  are,  however,  no  physical 
analogies  by  which  we  can  explain  the  connection  between 
the  physical  and  the  mental,  between  body  and  mind. 
The  so-called  connection  is,  in  reality,  as  I  believe,  identity. 
Viewed  from  without,  we  have  a  series  of  physical  and 
physiological  phenomena ;  felt  from  within,  we  have  a 
series  of  mental  and  psychological  phenomena.  It  is  the 
same  series  viewed  from  different  aspects.  This  is  no 
explanation ;  it  is  merely  a  way,  and,  as  I  believe,  the 
correct  way,  of  stating  the  facts.  Why  certain  physiological 
phenomena  should  have  a  totally  different  aspect  to  the 
organism  in  which  they  occur  from  that  which  they  offer 
to  one  who  watches  them  from  without,  is  a  question  which 
I  hold  to  be  insoluble.  All  we  have  to  remember,  however, 
is  that,  in  passing  from  the  mental  to  the  physical,  we  are 
changing  our  point  of  view.  The  series  may  be  set  down 
thus — 

External  aspect :  Physical  stimulus ^>aterneural  processes  — ^ actiyities. 
Inner  aspect:  Accompanying  consciousfJRT^- mental  states  — ^  accompany- 
ing consciousness. 

The  physical  stimulus  and  the  resulting  activities  are 

2E 


418  Animal  Life  and  Intelligence. 

occurrences  in  the  external  world,  and  more  or  less  lie 
open  to  our  view.  But  the  intervening  physical  and 
physiological  neural  processes  are  hidden  from  us.  As 
occurring  in  ourselves,  however,  tthe  mental  states  which 
are  the  inner  aspects  of  these  neural  processes  stand  out 
clearly  in  the  light  of  consciousness.  When,  therefore,  we 
are  watching  the  life-activities  of  others,  we  naturally  fill 
in  between  the  physical  stimulus  and  the  activities,  not  the 
neural  processes  of  which  we  are  so  ignorant,  but  mental 
states  analogous  to  those  of  which  we  are  conscious  under 
similar  conditions.  Thus  we  leap  from  the  physical  to  the 
mental,  and  back  again  to  the  physical,  as  represented  by 
the  diagonal  lines  in  the  above  scheme.  And  there  can  be 
no  objection  to  our  doing  so  if  we  bear  in  mind  that  we 
are  thus  changing  our  point  of  view. 

The  human  organism,  then — for  at  present  we  may 
regard  the  matter  from  man's  own  position — is  a  wonder- 
fully delicate  piece  of  organization,  with  mental  (inner) 
and  physical  (outer)  aspects.  It  is  in  a  condition  of  the 
most  delicate  equipoise.  Under  the  influence  of  a  percep- 
tion associated  with  an  appetence,  or  of  a  conception 
accompanied  by  a  desire,  it  is  thrown  into  a  state  of 
unstable  equilibrium ;  the  performance  of  the  action  which 
leads  to  the  fulfilment  or  satisfaction  of  the  appetence  or 
the  desire  restores  the  stability  of  the  system.  The  in- 
stability is  caused  by  the  conjoint  action  of  an  attraction 
towards  some  state  represented  as  desirable,  and  a  repul- 
sion from  the  existing  state  which  is  relatively  undesirable. 
In  some  cases  the  attraction,  and  in  others  the  repulsion,  is 
predominant.  When  we  are -in  an  uncomfortable  position, 
the  discomfort  is  predominant,  and  we  seek  relief  by 
changing  our  attitude.  When  the  bright  sunshine  tempts 
us  to  go  out  for  a  walk,  the  attraction  is  predominant.  But 
if  the  uncomfortable  attitude  is  enforced  and  prolonged,  we 
have  a  mental  representation  of  the  relief  we  long  for ;  and 
this  is  attractive.  And  if  we  have  work  which  keeps  us 
indoors,  the  irksome  restraint  brings  with  it  an  aversion  to 
our  present  lot. 


Habit  and  Instinct.  419 

Inseparably  associated  with  the  appetence  or  aversion 
there  is  a  representation  of  the  activity  which  constitutes 
the  fulfilment  of  the  emotion.  On  the  physiological  side 
this  is  probably  an  incipient  excitation  of  the  muscles  or 
other  organs  concerned  in  the  requisite  actions.  The 
miser's  fingers  itch  to  clutch  the  gold,  the  possession  of 
which  he  desires.  Our  muscles  twitch  as  we  long  to  join 
in  the  race  or  the  active  contention  of  a  game  of  football. 
Our  horse  grows  restive  as  the  hunt  goes  by.  Our  dog  can 
scarce  restrain  himself  from  racing  after  the  rabbits  in  the 
park.  Under  the  influence  of  emotion,  then,  the  body  is 
prepared  for  activity,  the  organs  and  muscles  are  beginning 
to  be  innervated,  and,  if  the  appetence  or  desire  be 
sufficiently  strong,  the  appropriate  actions  are  initiated, 
and  the  organism  tends  to  pass  from  the  state  of  unstable 
equilibrium  arising  out  of  a  pressing  need  to  the  stable 
condition  of  satisfied  appetence.  The  function  of  the  will 
in  this  process  we  shall  have  briefly  to  consider  presently. 

Let  us  here  notice,  with  regard  to  the  activities,  what 
we  have  before  seen  with  regard  to  the  process  of  perceptual 
construction.  We  there  noticed  that,  at  the  bidding  of  a 
relatively  simple  suggestion,  a  complex  object  may  be  con- 
structed by  the  mind.  This  presupposes  a  highly  com- 
plex mental  organization  ready  to  be  set  in  motion  by  the 
appropriate  stimulus.  The  organization  has  been. estab- 
lished by  association  and  through  evolution  in  the  indi- 
vidual and  his  ancestors.  It  is  the  same  with  the  activities. 
They,  too,  are  the  outcomes  of  associations  and  experiences 
established  and  registered  during  generations  of  ancestral 
predecessors.  At  the  bidding  of  the  appropriate  stimulus 
arousing  impulse  or  appetence,  a  train  of  activities  of  great 
intricacy  may  be  set  agoing  with  remarkable  accuracy  and 
precision.  It  is  true  that  a  certain  amount  of  individual 
education  is  required  to  draw  out  and  establish  the  latent 
powers  of  the  body,  as  also  of  the  mind ;  but  the  ability  is 
inborn,  and  only  requires  to  be  cultivated.  Every  one  of 
us  inherits  an  organization  rendering  him  capable  of  per- 
forming a  vast  amount  of  mental  construction  and  a  great 


42b  Animal  Life  and  Intelligence. 

number  of  bodily  activities.  All  he  has  to  do  is  to  learn 
how  to  use  it  and  to  make  himself  master  of  the  powers 
that  are  given  him. 

At  first,  the  acquisition  of  this  mastery  over  the  innate 
powers,  even  in  the  performance  of  comparatively  simple 
muscular  adjustments,  may  require  a  good  deal  of  attention 
and  practice.  But,  as  time  goes  on,  the  frequent  repetition 
of  the  ordinary  activities  of  everyday  life  leads  to  their 
easier  and  easier  performance.  In  simple  responsive 
actions  the  appropriate  activity  follows  readily  on  the 
appropriate  stimulus.  And,  ere  long,  many  acts  which  at 
first  required  intelligent  attention  are  performed  easily 
and  without  consciousness  of  effort  or  definite  intention. 
A  close  association  between  certain  oft-recurring  stimuli 
and. the  appropriate  response  in  activity  is  thus  established, 
and  the  action  follows  on  the  stimulus  without  hesitation  or 
trouble.  With  fuller  experience  and  further  practice  in  the 
ordinary  avocations  of  life,  the  responsive  activities  link 
themselves  more  and  more  closely  in  association,  become 
more  and  more  complex,  are  combined  in  series  and  classes 
of  activity  of  greater  length  and  accuracy,  and  thus  become 
organized  into  habits.  Under  this  head  fall  those  activities 
which  we  learn  with  difficulty  in  childhood,  and  perform 
with  ease  in  after-life.  At  first  voluntary  and  intentional, 
they  have  become,  or  are  becoming,  through  frequency 
and  uniformity  of  performance,  more  or  less  involuntary 
and  unintentional. 

"  The  work  of  the  world  is,"  we  are  told,  "  for  the  most 
part  done  by  people  of  whom  nobody  ever  hears.  The 
political  machine  and  the  social  machine  are  under  the 
ostensible  control  of  personages  who  are  well  to  the  front ; 
but  these  brilliant  beings  would  be  sorely  perplexed,  and 
the  machinery  would  soon  come  to  a  standstill,  but  for 
certain  experienced,  unambitious,  and  unobtrusive  members 
of  society."  So  is  it  also  in  the  economy  of  animal  life. 
The  work  of  life  is — to  paraphrase  Mr.  Norris's  words — for 
the  most  part  done  by  habits  of  which  nobody  ever  thinks. 
The  bodily  organization  is  ostensibly  under  the  control  of 


Habit  and  Instinct.  421 

intellect  and  reason ;  but  these  brilliant  qualities  would  be 
sorely  perplexed,  and  the  machinery  would  soon  come  to  a 
standstill,  but  for  certain  unobtrusive,  habitual  activities 
which  are  already  as  well  trained  in  the  routine  work  of 
life  as  are  the  permanent  clerks  in  the  routine  work  of  a 
Government  office. 

The  importance  of  the  establishment  of  these  habitual 
activities  is  immense.  As  the  muscular  and  other  re- 
sponses of  ordinary  everyday  life  become  habitual,  the 
mind  is,  so  to  speak,  set  free  from  any  special  care  with 
regard  to  their  regulation  and  co-ordination,  and  can  be 
concentrated  on  the  end  to  be  attained  by  such  activities. 
The  cat  that  is  creeping  stealthily  upon  the  bird  has  all 
her  attention  ri vetted  on  the  object  of  her  appetence,  and 
has  not  to  trouble  herself  about  the  movements  of  her 
body  and  limbs.  When  the  swallows  are  wheeling  over 
our  heads  in  the  summer  air,  their  sweeping  curves  and 
graceful  evolutions  are  not  the  outcome  of  careful  planning, 
but  are  just  the  normal  exercise  of  activities  which  from 
long  practice  have  become  habitual.  To  swim,  to  skate, 
to  cycle,  to  row,  to  play  the  piano^  or  the  violin, — all  these 
require  our  full  attention  at  first.  But  with  practice  they 
become  habitual,  and  during  their  performance  the  atten- 
tion may  be  devoted  to  quite  other  matters.  This  is  a 
great  gain.  Without  it  complex  trains  of  activities  could 
not  be  performed  with  ease  by  man  or  beast. 

When  once  habits  have  been  firmly  established,  their 
normal  performance  is  accompanied  by  a  sense  of  satisfac- 
tion. But  if  their  performance  is  prevented  or  thwarted, 
there  arises  a  sense  of  want  or  dissatisfaction.  The  pining 
of  a  caged  wild  animal  for  liberty  is  a  craving  for  the  free 
performance  of  its  habitual  activities.  In  an  animal  born 
into  captivity  the  craving  is  probably  less  intense,  though, 
for  reasons  which  will  presently  become  evident,  it  is 
presumably  by  no  means  absent.  Animals  are,  to  a  very 
large  extent,  creatures  of  habit.  Much  of  the  pleasure  of 
their  existence  lies  in  the  performance  of  habitual  activities. 
Our  zoological  gardens,  interesting  as  they  are  to  us,  are 


422  Animal  Life  and  Intelligence. 

probably  centres  of  an  amount  of  misery  and  discomfort, 
from  unfulfilled  promptings  of  habit  and  instinct,  which 
we  can  hardly  realize. 

From  habitual  activities  we  may  pass  by  easy  steps  to 
those  which  are  instinctive.  Both  habits  and  instincts, 
or,  to  use  a  more  convenient  and  satisfactory  mode  of 
expression  for  our  present  purpose,  both  habitual  and 
instinctive  activities,  are  based  upon  innate  capacity.  But 
whereas  habitual  activities  always  require  some  learning 
and  practice,  and  very  often  some  intelligence,  on  the  part 
of  the  individual,  instinctive  activities  are  performed  with- 
out instruction  or  training,  through  the  exercise  of  no 
intelligent  adaptation  on  the  part  of  the  performer,  and 
either  at  once  and  without  practice  (perfect  instincts)  or 
by  self-suggested  trial  and  practice  (incomplete  instincts).* 

There  is  some  little  difficulty  in  distinguishing  between 
instinctive  activities  and  reflex  actions.  Mr.  Herbert 
Spencer  defines  or  describes  instinct  as  compound  reflex 
action.  Mr.  Komanes  defines  instinct  as  reflex  action 
into  which  there  is  imported  the  element  of  consciousness. 
But,  on  the  one  hand,  many  instincts  involve  something 
more  than  compound  reflex  action,  since  there  is  an 
organized  sequence  of  activities ;  and,  on  the  other  hand, 
the  difficulty  (which  Mr.  Romanes  admits)  or  impossibility 
(as  I  contend)  of  applying  the  criterion  of  consciousness 
renders  unsatisfactory  the  introduction  of  the  mental 
element  as  distinctive.  I  would  say,  therefore,  that  (1) 
reflex  actions  are  those  comparatively  isolated  activities 
which  are  of  the  nature  of  organic  or  physiological  re- 
sponses to  more  or  less  definite  stimuli,  and  which  involve 
rather  the  several  organs  of  the  organism  than  the  activities 
of  the  organism  as  a  whole;  and  that  (2)  instinctive 
activities  are  those  organized  trains  or  sequences  of  co- 
ordinated activities  which  are  performed  by  the  individual 

*  I  use  the  term  "  incomplete,"  and  not  "imperfect,"  because  Mr.  Romanes, 
in  his  admirable  discussion  of  the  subject,  applies  the  term  "imperfect 
instinct "  to  cases  where  the  instinct  is  not  perfectly  adapted  to  the  end  in 
view  (see  "Mental  Evolution  in  Animals,"  p.  167). 


Habit  and  Instinct.  423 

in  common  with  all  the  members  of  the  same  more  or  less 
restricted  group,  in  adaptation  to  certain  circumstances, 
oft-recurring  or  essential  to  the  continuance  of  the  species. 

These  instinctive  activities  may,  as  I  have  said,  be  per- 
formed at  once  and  without  practice  (perfect  instincts)  or 
by  self -suggested  trial  and  practice  (incomplete  instincts). 
Most  young  mammals  require  some  little  practice  in  the 
use  of  their  limbs  before  they  are  able  to  walk  or  run. 
But  young  pigs  run  about  instinctively  so  soon  as  they  are 
born.  Thunberg,  the  South  African  traveller,  relates,  on 
the  testimony  of  an  experienced  hunter,  the  case  of  a 
female  hippopotamus  which  was  shot  the  moment  she  had 
given  birth  to  a  calf.  "  The  Hottentots,"  he  said,  "  who 
imagined  that  after  this  they  could  catch  the  calf  alive, 
immediately  rushed  out  of  their  hiding-place  to  lay  hold  of 
it ;  but,  though  there  were  several  of  them,  the  new-born 
calf  got  away  from  them,  and  at  once  made  the  best  of  its 
way  to  the  river." 

Even  in  cases  where  some  practice  is  apparently  neces- 
sary, the  activities  may  be,  and  often  are,  perfectly  in- 
stinctive. They  cannot,  however,  be  performed  immediately 
on  birth,  because  the  nervous  and  muscular  mechanism 
is  not  at  that  time  sufficiently  developed.  They  might, 
perhaps,  with  advantage  be  termed  "deferred  instincts." 
If  time  be  given  for  this  development,  the  activities  are 
carried  out  at  once  and  without  practice.  Throw  a  new- 
born puppy  into  the  river,  and,  after  some  helpless 
floundering,  he  will  be  drowned.  Throw  his  brother  when 
fully  grown  into  the  river,  and,  though  he  may  never  have 
been  in  the  water  in  his  life,  he  will  swim  to  shore.  He 
has  not  to  learn  to  swim ;  this  is  with  him  an  instinctive 
activity.  The  dog  inherits  the  power  which  the  boy  must 
with  some  little  difficulty  acquire.  He  probably  has  to 
pay  no  special  attention  to  the  muscular  adjustments 
involved.  The  act  is  accompanied  by  consciousness,  but 
not  that  directed  consciousness  we  call  "  attention."  When 
the  boy  has  acquired  the  habit,  he  is  scarcely  conscious  of 
the  special  muscular  co-ordinations  as  he  swims  across  the 


424  Animal  Life  and  Intelligence. 

river ;  he  is  only  conscious  of  a  desire  to  pick  the  water- 
lilies  near  the  further  bank. 

Birds,  especially  those  which  are  called  proecoces,  in 
contradistinction  from  the  altrices,  which  are  hatched  in  a 
helpless,  callow  condition,  come  into  the  world  prepared  at 
once  to  perform  complex  activities.  Mr.  Spalding  writes,* 
"  A  chicken  that  had  been  made  the  subject  of  experiments 
on  hearing  [having  been  blindfolded  at  birth]  was  un- 
hooded  when  nearly  three  days  old.  For  six  minutes  it 
sat  chirping  and  looking  about  it ;  at  the  end  of  that  time 
it  followed  with  its  head  and  eyes  the  movements  of  a  fly 
twelve, inches  distant;  at  ten  minutes  it  made  a  peck  at 
its  own  toes,  and  the  next  instant  it  made  a  vigorous  dart 
at  the  fly,  which  had  come  within  reach  of  its  neck,  and 
seized  and  swallowed  it  at  the  first  stroke ;  for  seven 
minutes  more  it  sat  calling  and  looking  about  it,  when  a 
hive-bee,  coming  sufficiently  near,  was  seized  at  a  dart, 
and  thrown  some  distance  much  disabled.  For  twenty 
minutes  it  sat  on  the  spot  where  its  eyes  had  been  unveiled 
without  attempting  to  walk  a  step.  It  was  then  placed  on 
rough  ground,  within  sight  and  call  of  a  hen  with  a  brood 
of  its  own  age.  After  standing  chirping  for  about  a  minute, 
it  started  off  towards  the  hen,  displaying  as  keen  a  percep- 
tion of  the  qualities  of  the  outer  world  as  it  was  ever  likely 
to  possess  in  after-life.  It  never  required  to  knock  its 
head  against  a  stone  to  discover  that  there  was  '  no  road 
that  way.'  It  leaped  over  the  smaller  obstacles  that  lay  in 
its  path,  and  ran  round  the  larger,  reaching  the  mother  in 
as  nearly  straight  a  line  as  the  nature  of  the  ground  would 
permit.  This,  let  it  be  remembered,  was  the  first  time  it 
had  ever  walked  by  sight. "f 

Mr.    Spalding's  experiments   also    proved    that,    even 

*  Macmillan's  Magazine,  February,  1873.  Professor  Eimer,  in  his  "  Organic 
Evolution"  (English  translation,  p.  245),  narrates  similar  experiences. 

t  Mr.  W.  Larden  states,  in  Nature  (vol.  xlii.),  that  his  brother  extracted, 
from  the  oviduct  of  a  Vivora  de  la  Cruz  snake  in  the  West  Indies,  two  young 
snakelets  six  inches  long.  Both,  though  thus  from  their  mother's  oviduct 
untimely  ripped,  threatened  to  strike,  and  made  the  burring  noise  with  the 
tail,  characteristic  of  the  snake. 


Habit  and  Instinct.  425 

among  the  altrices,  young  birds  do  not  require  to  be  taught 
to  fly,  but  fly  instinctively  so  soon  as  the  bodily  organiza- 
tion is  sufficiently  developed  to  render  this  activity  possible. 
He  kept  young  swallows  caged  until  they  were  fully  fledged, 
and  then  allowed  them  to  escape.  They  flew  straight  off 
at  the  first  attempt.  They  exhibited  the  instinctive  power 
of  flight  in  a  perfect  but  deferred  form. 

It  is,  however,  among  the  higher  invertebrates — • 
especially  among  the  insects,  and  of  them  pre-eminently 
in  the  social  hymenoptera,  ants  and  bees,  that  the  most 
remarkable  and  complete  instincts  are  seen.  There  is, 
however,  a  tendency  to  ascribe  all  the  habits  of  ants  and 
bees  to  instinct,  often,  as  it  seems  to  me,  without  sufficient 
evidence  that  they  are  performed  without  instruction,  and 
through  no  imitation  or  intelligent  adjustment.  This  is, 
perhaps,  a  survival  of  the  old-fashioned  view  that  all  the 
mental  activities  of  the  lower  animals  are  performed  from 
instinct,  whereas  all  the  activities  of  human  beings  are  to 
be  regarded  as  rational  or  intelligent.  In  popular  writings 
and  lectures,  for  example,  we  frequently  find  some  or  all  of 
the  following  activities  of  ant-life  ascribed  to  instinct : 
recognition  of  members  of  the  same  nest ;  powers  of  com- 
munication; keeping  aphides  for  the  sake  of  their  sweet 
secretion ;  collection  of  aphid  eggs  in  October,  hatching 
them  out  in  the  nest,  and  taking  them  in  the  spring  to  the 
daisies,  on  which  they  feed,  for  pasture  ;  slave-making  and 
slave-keeping,  which,  in  some  cases,  is  so  ancient  a  habit 
that  the  enslavers  are  unable  even  to  feed  themselves  ; 
keeping  insects  as  beasts  of  burden,  e.g.  a  kind  of  plant-bug 
to  carry  leaves ;  keeping  beetles,  etc.,  as  domestic  pets ; 
habits  of  personal  cleanliness,  one  ant  giving  another  a 
brush-up,  and  being  brushed-up  in  return ;  habits  of  play 
and  recreation  ;  habits  of  burying  the. dead;  the  storage  of 
grain  and  nipping  the  budding  rootlet  to  prevent  further 
germination ;  the  habits  described  by  Dr.  Lincecum,  and 
to  a  large  extent  confirmed  by  Dr.  McCook,*  that  Texan 

*  Dr.  McCook  confirms  the  observation  that  the  clearings  are  kept  clean, 
that  the  ant-rice  alone  is  permitted  to  grow  on  them,  and  that  the  produce  of 


426  Animal  Life  and  Intelligence. 

ants  go  forth  into  the  prairie  to  seek  for  the  seeds  of  a  kind 
of  grass  of  which  they  are  particularly  fond,  and  that  they 
take  these  seeds  to  a  clearing  which  they  have  prepared, 
and  then  sow  them  for  the  purpose,  six  months  afterwards, 
of  reaping  the  grain  which  is  the  produce  of  their  agricul- 
ture ;  the  collection  by  other  ants  of  grass  to  form  a  kind 
of  soil  on  which  there  subsequently  grows  a  species  of 
fungus  upon  which  they  feed  ;  the  military  organization  of 
the  ecitons  of  Central  America ;  and  so  forth.  Now,  the 
description  of  the  habits  of  ants  forms  one  of  the  most 
interesting  chapters  in  natural  history.  But  to  lump  them 
together  in  this  way,  as  illustrations  of  instinct,  is  a  survival 
of  an  old-fashioned  method  of  treatment.  That  they  have 
to  a  very  large  extent  an  innate  basis  may  be  readily 
admitted.  But  at  present  we  are  hardly  in  a  position  to 
say  how  far  they  are  instinctive,  that  is,  performed  by  each 
individual  straight  off,  and  without  imitation,  instruction, 
or  intelligence ;  how  far  habitual,  that  is,  performed  after 
some  little  training  and  practice ;  how  far  there  is  the 
intelligent  element  of  special  adaptation  to  special  circum- 
stances ;  how  far  they  are  the  result  of  imitation ;  to  what 
extent,  if  any,  individual  training  and  instruction  are  factors 
in  the  process. 

To''put  the  matter  in  another  way.  Suppose  that  an 
intelligent  ant  were  to  make  observations  on  human 
activities  as  displayed  in  one  of  our  great '  cities  or  in  an 
agricultural  district.  Seeing  so  great  an  amount  of  routine 
work  going  on  around  him,  might  he  not  be  in  danger  of 
regarding  all  this  as  evidence  of  blind  instinct  ?  Might  he 
not  find  it  difficult  to  obtain  satisfactory  evidence  of  the 
establishment  of  our  habits,  of  the  fact  that  this  routine 
work  has  to  some  extent  to  be  learnt  ?  Might  he  not  say 
(perhaps  not  wholly  without  truth),  "I  can  see  nothing 
whatever  in  the  training  of  the  children  of  these  men  to  fit 
them  for  their  life-activities.  The  training  of  their  children 

this  crop  is  carefully  harvested ;  but  he  thinks  that  the  ant-rice  sows  itself, 
and  is  not  actually  planted  by  the  ants  (see  Sir  John  Lubbock's  "  Scientific 
Lectures,"  2nd  edit.,  p.  112).  ; 


Habit  and  Instinct.  427 

has  no  more  apparent  bearing  upon  the  activities  of  their 
after-life  than  the  feeding  of  our  grubs  has  on  the  duties  of 
ant-life.  And  although  we  must  remember,"  he  might 
continue,  "that  these  large  animals  do  not  have  the 
advantage  which  we  possess  of  awaking  suddenly,  as  by  a 
new  birth,  to  their  full  faculties,  still,  as  they  grow  older, 
now  one  and  now  another  of  their  instinctive  activities  are 
unfolded  and  manifested.  They  fall  into  the  routine  of  life 
with  little  or  no  training  as  the  period  proper  to  the  various 
instincts  arrives.  If  learning  thereof  there  be,  it  has  at 
present  escaped  our  observation.  And  such  intelligence  as 
their  activities  evince  (and  many  of  them  do  show  remark- 
able adaptation  to  uniform  conditions  of  life)  would  seem 
to  be  rather  ancestral  than  of  the  present  time ;  as  is 
shown  by  the  fact  that  many  of  the  adaptations  are  directed 
rather  to  past  conditions  of  life  than  to  those  which  now 
hold  good.  In  the  presence  of  new  emergencies  to  which 
their  instincts  have  not  fitted  them,  these  poor  men  are 
often  completely  at  a  loss.  We  cannot  but  conclude,  there- 
fore, that,  although  shown  under  somewhat  different  and 
less  favourable  conditions,  instinct  occupies  fully  as  large 
a  space  in  the  psychology  of  man  as  it  does  in  that  of  the 
ant,  while  their  intelligence  is  far  less  unerring  and,  there- 
fore, markedly  inferior  to  our  own." 

Of  course,  the  views  here  attributed  to  the  ant  are  very 
absurd.  But  are  they  much  more  absurd  than  the  views 
of  those  who,  on  the  evidence  which  we  at  present  possess, 
attribute  all  the  varied  activities  of  ant-life  to  instinct  ? 
Take  the  case  of  the  ecitons,  or  military  ants,  or  the 
harvesting  ants,  or  the  ants  that  keep  draught-bugs  as 
beasts  of  burden :  have  we  sufficient  evidence  to  enable 
us  to  affirm  that  these  activities  are  purely  instinctive  and 
not  habitual  ?  That  they  are  to  a  large  extent  innate,  few 
are  likely  to  deny ;  but  then  our  own  habitual  acts  have  a 
basis  that  is,  to  a  very  large  extent,  innate.  The  question 
is  not  whether  they  have  an  innate  basis,  but  whether 
all  the  varied  manoeuvres  of  the  military  ants,  for  example, 
are  displayed  to  the  full  without  any  learning  or  imitation, 


428  .Animal  Life  and  Intelligence. 

without  teaching  and  without  intelligence  on  the  part  of 
every  individual  in  the  army.* 

That  in  some  cases  there  is  something  very  like  a  train- 
ing or  education  of  the  ant  when  it  emerges  from  the  pupa 
condition  is  rendered  probable  by  the  observations  of 
M.  Forel.  As  Mr.  Eomanes  says,t  "  The  young  ant  does 
not  appear  to  come  into  the  world  with  a  full  instinctive 
knowledge  of  all  its  duties  as  a  member  of  a  social  com- 
munity. It  is  led  about  the  nest  and  '  trained  to  a  know- 
ledge of  domestic  duties,  especially  in  the  case  of  larvae.' 
Later  on,  the  young  ants  are  taught  to  distinguish  between 
friends  and  foes.  When  an  ants'  nest  is  attacked  by 
foreign  ants,  the  young  ones  never  join  in  the  fight,  but 
confine  themselves  to  removing  the  pupse;  and  that  the 
knowledge  of  hereditary  enemies  is  not  wholly  instinctive 
in  ants  is  proved  by  the  following  experiment,  which  we 
owe  to  Forel.  He  put  young  ants  belonging  to  three 
different  species  into  a  glass  case  with  pupae  of  six  other 
species — all  the  species  being  naturally  hostile  to  one 
another.  The  young  ants  did  not  quarrel,  but  worked 
together  to  tend  the  pupae.  When  the  latter  hatched  out, 
an  artificial  colony  was  formed  of  a  number  of  naturally 
hostile  species,  all  living  together  after  the  manner  of  the 
*  happy  families '  of  the  showmen." 

I  have  said  that  the  varied  activities  of  ants,  though 
they  may  not  in  all  cases  be  truly  instinctive,  are  never- 
theless the  outcome  of  certain  innate  capacities.  It  seems 
to  me  necessary  to  distinguish  carefully  between  innate 

*  The  experiments,  both  of  Sir  John  Lubbock  and  Mr.  Komanes,  show 
that  the  homing  instinct  of  bees  is  largely  the  result  of  individual  obser- 
vation. Taken  to  the  seashore  at  no  great  distance  from  the  hive,  where 
the  objects  around  them,  however,  were  unfamiliar  (since  the  seashore  is  not 
the  place  were  flowers  and  nectar  are  to  be  found),  the  ,bees  were  nonplussed 
and  lost  their  way.  Similarly,  the  migration  of  birds  "  is  now,"  according  to 
Mr.  Wallace,  "well  ascertained  to  be  effected  by  means  of  vision,  long  flights 
being  made  on  bright  moonlight  nights,  when  the  birds  fly  very  high,  while 
on  cloudy  nights  they  fly  low,  and  then  often  lose  their  way"  ("Darwinism," 
p.  442).  This,  of  course,  does  not  explain  the  migratory  instinct — the  internal 
prompting  to  migrate — but  it  indicates  that  the  carrying  out  of  the  migratory 
impulse  is,  in  part  at  least,  intelligent. 

t  "  Auimal  Intelligence,"  p.  59. 


Habit  and  Instinct.  429 

capacity  and  instinct.  Every  animal  comes  into  the  world 
with  an  innate  capacity  to  perform  the  activities  which 
have  been  necessary  for  the  maintenance  of  the  normal 
existence  of  its  ancestors.  This  is  part  of  its  inherited 
organization.  Only  when  these  activities  are  performed  at 
the  bidding  of  impulse,  through  no  instruction  and  from 
no  tendency  to  imitation,  can  they,  strictly  speaking,  be 
termed  instinctive.  The  more  uniform  the  conditions  of 
ancestral  life,  and  the  more  highly  developed  the  organism 
when  it  enters  upon  the  scene  of  active  existence,  the  more 
likely  are  the  innate  capacities  to  manifest  themselves  at 
once  and  without  training  as  perfect  instincts.  Among 
birds,  the  prcecoces,  which  reach  a  high  state  of  develop- 
ment within  the  egg,  and  among  insects,  those  which 
undergo  complete  metamorphosis,  and  emerge  from  the 
pupa  or  chrysalis  condition  fully  formed  and  fully  equipped 
for  life,  display  the  greatest  tendency  to  exhibit  activities 
which  are  truly  and  perfectly  instinctive.  But  man,  whose 
ancestors  have  lived  and  worked  under  such  complex  con- 
ditions, and  who  comes  into  the  world  in  so  helpless  and 
immature  a  state,  though  his  innate  capacities  are 
enormous,  exhibits  but  few  and  rudimentary  instincts. 

One  marked  characteristic  of  many  of  the  habits  and 
instincts  of  the  lower  animals  is  the  large  amount  of  blind 
prevision  (if  one  may  be  allowed  the  expression)  which 
they  display.  By  blind  prevision  I  mean  that  preparation 
for  the  future  which,  if  performed  through  intelligence  or 
reason,  we  should  term  "  foresight,"  but  which,  since  it  is 
performed  prior  to  any  individual  experience  of  the  results, 
is  done,  we  must  suppose,  in  blind  obedience  to  the  internal 
impulse.  The  sphex,  a  kind  of  wasp-like  insect,  forms  a 
little  mud  chamber  in  which  she  lays  her  eggs.  She  goes 
forth,  finds  a  spider,  stings  it  in  such  a  way  that  it  is 
paralyzed  but  not  killed,  and  places  it  in  the  chamber  for 
her  unborn  young,  which  she  will  never  see.  The  hen 
incubates  her  eggs,  though  she  may  never  have  seen  a 
chicken  in  her  life.  The  caterpillars  of  an  African  moth 
weave  a  collective  cocoon  as  large  as  a  melon.  All  unite 


430  Animal  Life  and  Intelligence. 

to  weave  the  enveloping  husk;  each  forms  its  separate 
cocoon  within  the  shell,  and  all  these  separate  cocoons  are 
arranged  round  branch-passages  or  corridors,  by  which  the 
moths,  when  they  emerge  from  the  chrysalis  condition, 
may  escape.  Another  caterpillar,  that  of  a  butterfly 
(Thekla)  feeds  within  the  pomegranate,  but  with  silken 
threads  attaches  the  fruit  to  the  branch  of  the  tree,  lest, 
when  withered,  it  should  fall  before  the  metamorphosis  is 
complete.  An  ichneumon  fly,  mentioned  by  Kirby  and 
Spence,  "  deposits  its  eggs  in  the  body  of  a  larva  hidden 
between  the  scales  of  a  fir-cone,  which  it  can  never  have 
seen,  and  yet  knows  where  to  seek;  "  and  thus  provision  is 
made  for  young  which  it  will  never  know.  Instances  of 
such  blind  prevision  might  be  quoted  by  the  score.  It  is 
idle  to  speculate  as  to  the  accompaniments  of  consciousness 
of  such  acts.  If  it  be  asked — May  there  not  be  associated 
with  the  performance  of  the  instinctive  activity  of  incuba- 
tion an  inherited  memory  of  a  generalized  chick  ?  we  can 
only  answer  that  we  do  not  know,  but  that  we  guess  not.* 

There  is,  however,  one  association,  in  the  case  of  these 
and  other  instincts,  which  we  may  fairly  surmise  to  be 
frequent,  though,  for  reasons  to  be  specified  hereafter,  it  is 
probably  not  invariable.  Just  as  we  saw  to  be  the  case 
with  habits,  so  too  with  instinctive  activities,  their  per- 
formance is  not  infrequently  associated  with  pleasurable 
feeling,  their  non-performance  with  pain  and  discomfort 
and  a  sense  of  craving  or  want.  The  animal  prevented 
from  performing  its  instinctive  activities  is  often  apparently 
unquiet,  uneasy,  and  distressed.  Hence  I  said  that  the 
animals  in  our  zoological  gardens,  even  if  born  and  reared 
in  captivity,  may  exhibit  a  craving  for  freedom  and  a 
yearning  to  perform  their  instinctive  activities.  This 
craving  may  be  regarded  as  a  blind  and  vague  impulse, 
prompting  the  animal  to  perform  those  activities  which  are 
for  its  own  good  and  for  the  good  of  the  race  to  which  it 
belongs.  The  satisfaction  of  the  craving,  the  gratification 

*  The  American  expression,  "  I  guess,"  is  often  far  truer  to  fact  than  its 
English  equivalent,  "  I  think." 


Habit  and  Instinct.  431 

of  the  blind  impulse,  is  accompanied  by  a  feeling  of  relief 
and  ease.  Thus  where  a  motive  emerges  at  all  into  con- 
sciousness, that  from  which  we  may  presume  that  instinctive 
activities  are  performed  is  not  any  foreknowledge  of  their 
end  and  purpose,  but  the  gratification  of  an  immediate 
and  pressing  need,  the  satisfaction  of  a  felt  want. 

We  have,   so    far,  been    concerned  merely  with   the 
various  kinds  of  activity  presented  by  men  and  animals, 
and  with  some  of  their  characteristics.     The  organism,  in 
virtue  of  its  organization,  has  an  inherited  groundwork  of 
innate  capacity.    Surrounding  circumstances  and  commerce 
with  the  world  draw  out  and  develop  the  activities  which 
the  innate   capacity  renders   possible.     First,  there   are 
automatic   and   reflex  actions,   which   are  comparatively 
isolated  activities  in  response  to  definite  stimuli,  external 
or  internal.     Secondly,  there  are  those  organized  trains  or 
sequences  of  co-ordinated  activities  which  are  performed 
by  the  individual  in  common  with  all  the  members  of  the 
same  more  or  less  restricted  group,  in  adaptation  to  certain 
circumstances,  oft-recurring  or  essential  to  the  continuance 
of  the  species.     These  are  the  instinctive  activities.     But 
no  hard-and-fast  line  can  be  drawn  between  them  and 
reflex  actions.     The  instinctive   activities  may  be   either 
perfect  or  relatively  imperfect,  according  to  the  accuracy 
of  their  adaptation  to  the  purpose  for  which  the  activity  is 
performed ;  but  in  either  case  they  are  carried  out  without 
learning  or  practice.     In  some  cases,  however,  they  cannot 
be  performed  until   the  organization   is   more  perfectly 
developed  than  it  is  at  birth ;  but  when  the  proper  time 
arrives  they  are  perfect,  and  require  no  practice;  these 
may  be  termed  "  deferred  instincts."     Where  some  practice, 
but  only  a  little,  is  required,  the  instinctive  activities  may 
be  regarded  as  incomplete ;   and  these  pass  into  those 
activities  which  require  at  first  a  good  deal  of  practice, 
learning,  and  attention,  but  eventually  run  off  smoothly 
and  without  special  attention,  at  times  almost  or  quite 
unconsciously.     These  are    habitual  activities.    Finally, 


432  Animal  Life  and  Intelligence. 

we  have  those  activities  which  are  performed  in  special 
adaptation  to  special  circumstances.  These  are  intelligent 
activities. 

All  of  these  may  be,  and  the  last,  the  intelligent  actions, 
invariably  are,  accompanied  by  consciousness.  The  habitual 
activities,  and  those  which  are  incompletely  instinctive,  are 
also,  we  may  presume,  accompanied  by  consciousness 
during  the  process  of  their  organization  and  establishment. 
It  is  possible,  however,  that  some  of  the  perfectly  instinctive 
activities  may  be  performed  unconsciously.  When  we 
consider  how  perfectly  organized  such  activities  are,  and 
when  we  also  remember  that  perfectly  organized  habitual 
activities  are  frequently  in  us  unconscious,  we  shall  see 
cause  for  suspecting  that  instinctive  activities  may,  at  any 
rate  in  some  cases,  be  unconscious.  No  doubt  the  con- 
ditions of  consciousness  are  not  well  understood.  But  let 
us  accept  Mr.  Eomanes's  suggestion,  that  a  physiological 
concomitant  is  ganglionic  delay.  "  Now  what,"  he  asks,* 
"  does  this  greater  consumption  of  time  imply  ?  It  clearly 
implies,"  he  answers,  "  that  the  nervous  mechanism  con- 
cerned has  not  been  fully  habituated  to  the  performance  of 
the  response  required,  and  therefore  that,  instead  of  the 
stimulus  merely  needing  to  touch  the  trigger  of  a  ready- 
formed  apparatus  of  response  (however  complex  this  may 
be),  it  has  to  give  rise  in  the  nerve-centre  to  a  play  of 
stimuli  before  the  appropriate  response  is  yielded.  In  the 
higher  planes  of  conscious  life  this  play  of  stimuli  in  the 
presence  of  difficult  circumstances  is  known  as  indecision ; 
but  even  in  a  simple  act  of  consciousness — such  as  signalling 
a  perception — more  time  is  required  by  the  cerebral 
hemispheres  in  supplying  an  appropriate  response  to  a 
non-habitual  experience,  than  is  required  by  the  lower 
nerve-centres  for  performing  the  most  complicated  of  reflex 
actions  by  way  of  response  to  their  habitual  experience. 
In  the  latter  case  the  routes  of  nervous  discharge  have 
been  well  worn  by  use;  in  the  former  case  these  routes 
have  to  be  determined  by  a  complex  play  of  forces  amid 

*  "  Mental  Evolution  in  Animals,"  pp.  73,  74. 


Habit  and  Instinct.  433 

the  cells  and  fibres  of  the  cerebral  hemispheres.  And  this 
complex  play  of  forces,  which  finds  its  physiological  ex- 
pression in  a  lengthening  of  the  time  of  latency,  finds  also 
a  psychological  expression  in  the  rise  of  consciousness." 
Now,  since  in  many  instinctive  activities  the  stimulus 
"  merely  needs  to  touch  the  trigger  of  a  ready-formed 
apparatus  of  response,"  I  think  that  they  may  be  uncon- 
scious. And  Mr.  Eomanes  thus  himself  supplies  the 
reason  for  rejecting  his  own  definition  of  instinct  as  "reflex 
action  into  which  there  is  imported  the  element  of  con- 
sciousness." Of  course,  logically,  Mr.  Eomanes  can  reply, 
"It  is  merely  a  question  of  where  we  draw  the  line ;  if  the 
activity  is  unconscious,  it  is  a  reflex  action ;  if  conscious, 
it  is  an  instinct."  I  think  this  unsatisfactory,  (1)  because 
the  criterion  of  consciousness,  from  its  purely  inferential 
nature,  is  practically  impossible  of  application  with 
accuracy ;  (2)  because  the  same  series  of  activities  may 
probably  at  one  time  be  unconscious  and  at  another  time 
conscious ;  and  (3)  because  many  actions  which  are  almost 
universally  regarded  as  reflex  actions  may  at  times  be 
accompanied  by  consciousness,  and  would  then  have,  on 
Mr.  Eomanes's  view,  to  be  regarded  as  instincts. 

Having  made  this  initial  criticism,  I  may  now  state 
that  I  regard  Mr.  Eomanes's  treatment  of  instinct  as  most 
admirable  and  masterly.  Building  upon  the  foundation 
laid  by  Charles  Darwin,  he  has  worked  out  the  theory  of 
instinct  in  a  manner  at  once  broad  and  yet  minute,  lucid 
and  yet  close,  definite  in  doctrine  and  yet  not  blind  to 
difficulties.  If  I  say  that  it  is  a  piece  of  work  worthy  of 
the  great  master  whose  devoted  disciple  Mr.  Eomanes  has 
proved  himself,  I  am  according  it  the  highest  praise  in  my 
power.  I  have  ventured  in  this  volume  to  criticize  some 
of  Mr.  Eomanes's  conclusions  in  the  field  of  animal  in- 
telligence. And  lest  I  should  seem  to  undervalue  his 
work,  lest  our  few  divergences  should  seem  to  hide  our 
many  parallelisms,  I  take  this  opportunity  of  testifying 
to  my  great  and  sincere  admiration  of  the  results  of 
his  careful  and  exact  observations,  his  patient  and  thought- 

2F 


434  Animal  Life  and  Intelligence. 

ful  inferences,  and  his  lucid  and  often  luminous  expo- 
sition. 

I  do  not  propose  to  go  over  the  ground  so  exhaustively 
covered  by  Mr.  Romanes  in  his  discussion  of  instinct.  I 
shall  first  endeavour  shortly  to  set  forth  his  conclusions, 
and  then  review  the  suhject  in  the  light  of  modern  views  of 
heredity. 

Admitting  that  some  instincts  may  have  arisen  from 
the  growth,  extension,  and  co-ordination  of  reflex  actions, 
Mr.  Romanes  regards  the  majority  of  instincts  as  of  two- 
fold origin — first,  from  the  natural  selection  of  fortuitous 
unintelligent  activities  which  chanced  to  be  profitable  to 
the  agent  (primary  instincts) ;  and,  secondly,  from  the 
inheritance  of  habitual  activities  intelligently  acquired. 
These  are  the  secondary  instincts,  comprising  activities 
which  have  become  instinctive  through  lapsed  intelligence. 
In  illustration  of  primary  instincts,  Mr.  Romanes  cites  the 
instinct  of  incubation.  "It  is  quite  impossible,"  he  says,* 
"that  any  animal  can  ever  have  kept  its  eggs  warm  with 
the  intelligent  purpose  of  hatching  out  their  contents,  so 
that  we  can  only  suppose  that  the  incubating  instinct  began 
by  warm-blooded  animals  showing  that  kind  of  attention  to 
their  eggs  which  we  find  to  be  frequently  shown  by  cold- 
blooded animals.  .  .  .  Those  individuals  which  most  con- 
stantly cuddled  or  brooded  over  their  eggs  would,  other 
things  equal,  have  been  most  successful  in  rearing  progeny ; 
and  so  the  incubating  instinct  would  be  developed  without 
there  ever  having  been  any  intelligence  in  the  matter." 

Many  of  the  instincts  which  exhibit  what  I  have  termed 
above  "blind  prevision"  must,  it  would  seem,  belong 
completely  or  in  the  main  to  this  class.  The  instincts  of 
female  insects,  which  lead  them  to  anticipate  by  blind 
prevision  the  wants  of  offspring  they  will  never  see ;  the 
instincts  of  the  caterpillars,  which  lead  them  to  make  pro- 
vision for  the  chrysalis  or  imago  condition  of  which  they 
can  have  no  experience ;  the  instinct  of  a  copepod 
crustacean,  which  lays  its  eggs  in  a  brittle-star,  that  they 

*  "Mental  Evolution  in  Animals,"  p.  177. 


Habit  and  Instinct.  435 

may  therein  develop,  probably  in  the  brood- sac,  and  may 
even  destroy  the  reproductive  powers  of  the  host  for  the 
future  good  of  her  own  offspring — these  and  many  others 
would  seem  to  have  no  basis  in  individual  experience. 

In  illustration  of  the  second  class  of  instincts,  those 
due  to  lapsed  intelligence,  Mr.  Eomanes  cites  the  case  of 
birds  living  on  oceanic  islands,  which  at  first  show  no  fear 
of  man,  but  which  acquire  in  a  few  generations  an  instinc- 
tive dread  of  him — for  the  wildness  or  tameness  may 
become  truly  instinctive.  "If,"  says  Dr.  Kae,*  "the  eggs 
of  a  wild  duck  are  placed  with  those  of  a  tame  one  under  a 
hen  to  be  hatched,  the  ducklings  from  the  former,  on  the 
very  day  they  leave  the  egg,  will  immediately  endeavour 
to  hide  themselves,  or  take  to  the  water  if  there  is  any 
water,  should  any  person  approach,  whilst  the  young  from 
the  tame  duck's  eggs  will  show  little  or  no  alarm,  indicating 
in  both  cases  a  clear  instance  of  instinct  or  'inherited 
memory.' " 

It  must  not  be  supposed  that  these  two  modes  of  origin 
are  mutually  exclusive,  and  that  any  particular  instinct 
must  belong  either  to  the  one  class  or  the  other.  On  the 
contrary,  many  instincts  have,  as  it  were,  a  double  root — 
the  principle  of  selection  combining  with  that  of  lapsing 
intelligence  in  the  formation  of  a  joint  result.  Intelligence 
may  thus  give  a  new  direction  to  a  primary  instinct,  and, 
the  intelligent  modification  being  inherited,  what  is  prac- 
tically a  new  instinct  may  arise.  Conversely,  selection 
may  tend  to  preserve  those  individuals  which  perform 
some  intelligent  action,  and  may,  therefore,  aid  the  lapsing 
of  intelligence  in  establishing  and  stereotyping  an  instinct. 
Referring  the  reader  to  Mr.  Romanes's  work  for  the 
examples  and  illustrations  by  which  he  enforces  his  views, 
we  may  now  proceed  to  consider  the  subject  in  the  light  of 
recently  developed  theories  of  heredity. 

We  have  seen  that  a  school  of  biologists  has  arisen 
who  deny  the  inheritance  of  acquired  characters.     But  Mr. 

*  Nature,  vol.  xsviii.  p.  2712  quoted  in  "  Mental  Evolution  in  Animals," 
footnote,  p.  196. 


436  Animal  Life  and  Intelligence. 

Bomanes's  secondary  instincts  depend  upon  the  inheritance 
of  habits  intelligently  acquired.  By  the  school  of  Professor 
Weismann,  therefore  (if  we  may  so  call  it  "without  injustice 
to  Mr.  Francis  Galton),  secondary  instincts,  in  so  far  as 
any  individual  acquisition  is  concerned,  are  denied. 
Opposed  to  this  school  are  those  who  lay  great  stress  on 
the  inheritance  of  acquired  characters.  Some  of  them 
seem  driven  to  the  opposite  extreme  in  the  matter  of 
instinct,  and  appear  to  hold  that  instincts  are  entirely  (or 
let  us  say  almost  entirely)  due  to  lapsed  intelligence. 
Professor  Eimer,  of  Tubingen,  for  example,  says,*  "  I 
describe  as  automatic  actions  those  which,  originally  per- 
formed consciously  and  voluntarily,  in  consequence  of 
frequent  practice,  come  to  be  performed  unconsciously  and 
involuntarily.  .  .  .  Such  acquired  automatic  actions  can 
be  inherited.  Instinct  is  inherited  faculty,  especially  is 
inherited  habit."  In  his  discussion  of  the  subject,  Pro- 
fessor Eimer  seems  to  make  no  express  allusion  to  primary 
instincts.  And  he  regards  at  any  rate  some  of  those 
which  are  classed  by  Mr.  Eomanes  as  primary,  as  due  to 
lapsed  intelligence.  "Every  bird,"  he  says  f  "  must,  from 
the  first  time  it  hatches  its  eggs,  draw  the  conclusion  that 
young  will  also  be  produced  from  the  eggs  which  it  lays 
afterwards,  and  this  experience  must  have  been  inherited 
as  instinct."  He  says  %  .that  the  infant  takes  the  breast 
and  sucks  "  in  accordance  with  its  acquired  and  inherited 
faculties."  He  believes  §  that  "  the  original  progenitors  of 
our  cuckoo,  when  they  began  to  lay  their  eggs  in  other 
nests,  acted  by  reflection  and  with  design."  Kegarding  the 
mason-wasps  and  their  allies,  which  sting  larvaB  in  the 
ganglia  which  govern  muscular  action,  and  thus  provide 
their  young  with  paralyzed  but  living  prey,  he  exclaims,! 
"  What  a  wonderful  contrivance !  What  calculation  on 
the  part  of  the  animal  must  have  been  necessary  to  discover 
it !  "  Of  the  storing  instincts  of  bees  he  remarks, IT  "  Selec- 
tion cannot  here  have  had  much  influence,  since  the 

*  "  Organic  Evolution,"  pp.  223,  224.  t  Ibid.  p.  263. 

t  Ibid.  p.  303.         §  Ibid.  p.  258.        ||  Ibid.  p.  279.        1  Ibid.  p.  276. 


Habit  and  Instinct.  437 

workers  do  not  reproduce.  In  order  to  make  these  favour- 
able conditions  constant,  insight  and  reflection  on  the  part 
of  the]  animals,  and  inheritance  of  these  faculties,  were 
necessary."  And  he  concludes,*  "  Thus,  according  to  the 
preceding  considerations,  automatic  action  may  be  described 
as  habitual  voluntary  action ;  instinct,  as  inherited  habitual 
voluntary  action,  or  the  capacity  for  such  action." 

Professor  Eimer  would  not  probably  deny  the  co-opera- 
tion of  natural  selection  in  the  establishment  of  these 
instincts,  but  he  throws  it  altogether  into  the  background. 
Now,  such  a  view  seems  to  me  wholly  untenable.  Many  of 
the  instincts  of  insects  are  performed  only  once  in  the 
course  of  each  individual  life.  Can  it  be  supposed  that  the 
weaving  of  a  cocoon  by  the  caterpillar  is  mainly  a  matter 
of  lapsed  intelligence  ?  Even  if  we  credit  the  hen  bird 
with  the  amount  of  reflection  supposed  by  Professor  Eimer, 
can  we  grant  to  the  ancestors  of  the  ichneumon  fly  such 
far-reaching  observation  and  intelligence  as  really  to 
foresee  (not  by  blind  prevision,  but  through  intelligent 
foresight)  the  future  development  of  the  eggs  which  she 
lays  in  a  caterpillar  ?  Are  we  to  suppose  that  the  instinctive 
action  of  the  young  cuckoo,  which,  the  day  after  it  is  hatched, 
will  eject  all  the  other  occupants  of  a  hedge-accentor's 
nest,f  can  have  had  its  origin  in  lapsed  intelligence  ?  If, 
because  of  their  purposive  character,  we  are  to  regard  such 
instincts  as  of  intelligent  origin,  may  we  not  be  told  that 
through  intelligent  design  the  pike  has  beset  its  jaws, 
palate,  and  gill-arches  with  innumerable  teeth,  all  back- 
wardly  directed  for  the  purpose  of  holding  its  slippery  prey ; 
and  the  eagle  has  protected  its  eye  with  a  bony  ring  of 
sclerotic  plates,  like  the  holder  of  an  optician's  watch-glass? 
If  mimicry  in  form  and  colour  is  due  to  natural  selection, 
why  not  mimicry  in  habits  and  activities  ?  If  structures  of 
a  wonderfully  purposive  character  have  been  evolved  with- 

*  "  Organic  Evolution,"  p.  298.  The  late  G.  H.  Lewes  held  somewhat 
similar  views. 

t  See  Mr.  John  Hancock,  Natural  History  Transactions,  Northumberland, 
Durham,  and  Newcastle-on-Tyne,  vol.  viii.  (1886) ;  and  Nature,  vol.  xxxiii 
p.  519. 


43 8  Animal  Life  and  Intelligence. 

out  the  intelligent  co-operation  of  the  organisms  which 
possess  them,  why  not  some  of  the  highly  purposive 
activities  ? 

And  here  the  disciple  of  the  school  of  Professor  Weis- 
rnann  will  echo  and  extend  the  question,  and  will  say, 
"  Yes  !  why  not  all  instinctive  activities  ?  You  are  ready  to 
admit,"  he  will  continue,  "that  many  instincts,  wonderfully 
purposive  in  their  nature,  are  of  primary  origin,  that  is  due 
to  natural  selection ;  why,  then,  invoke  any  other  mode  of 
origin  ?  If  lapsed  intelligence  be  excluded  in  these  cases, 
why  introduce  it  at  all  ?  Why  not  admit,  what  our  theory 
of  heredity  demands,  that  *  '  all  instinct  is  entirely  due  to 
the  operation  of  natural  selection,  and  has  its  foundation, 
not  upon  inherited  experiences,  but  upon  the  variations  of 
the  germ'  ?" 

Professor  Weismann's  contention  needs  much  more 
serious  consideration  than  that  of  Professor  Eimer.  I 
think  there  is  force  in  the  a  priori  argument  (as  an  a  priori 
argument)  that  since  very  complex  instincts  are  probably 
of  primary  origin,  there  is  no  a  priori  necessity  for  the 
introduction  of  the  hypothesis  of  lapsed  intelligence.  Let 
me  first  illustrate  this  further. 

A  certain  beetle  (Sitaris)  lays  its  eggs  at  the  entrance 
of  the  galleries  excavated  by  a  kind  of  bee  (Anthophora) , 
each  gallery  leading  to  a  cell.  The  young  larvaB  are 
hatched  as  active  little  insects,  with  six  legs,  two  long 
antennae,  and  four  eyes,  very  different  from  the  lame  of 
other  beetles.  They  emerge  from  the  egg  in  the  autumn, 
and  remain  in  a  sluggish  condition  till  the  spring.  At  that 
time  (in  April)  the  drones  of  the  bee  emerge  from  the 
pupae,  and  as  they  pass  out  through  the  gallery  the  sitaris 
larvae  fasten  upon  them.  There  they  remain  till  the 
nuptial  flight  of  the  anthophora,  when  the  larva  passes 
from  the  male  to  the  female  bee.  Then  again  they  await 
their  chance.  The  moment  the  bee  lays  an  egg,  the  sitaris 
larva  springs  upon  it.  "  Even  while  the  poor  mother  is 
carefully  fastening  up  her  cell,  her  mortal  enemy  is  be- 

*  Weismanu,  "  On  Heredity,"  p.  91. 


Habit  and  Instinct.  439 

ginning  to  devour  her  offspring ;  for  the  egg  of  the 
anthophora  serves  not  only  as  a  raft,  but  as  a  repast. 
The  honey,  which  is  enough  for  either,  would  be  too  little 
for  both ;  and  the  sitaris,  therefore,  at  its  first  meal, 
relieves  itself  from  its  only  rival.  After  eight  days  the  egg 
is  consumed,  and  on  the  empty  shell  the  sitaris  undergoes 
its  first  transformation,  and  makes  its  appearance  in  a 
very  different  form.  ...  It  changes  into  a  white,  fleshy 
grub,  so  organized  as  to  float  on  the  surface  of  the  honey, 
with  the  mouth  beneath  and  the  spiracles  above  the 
surface.  ...  In  this  state  it  remains  until  the  honey  is 
consumed ;  "  *  and,  after  some  further  metamorphoses, 
develops  into  a  perfect  beetle  in  August. 

Now,  it  seems  to  me  difficult  to  understand  how,  at  any 
stage  of  this  long  series  of  highly  adaptive,  instinctive 
activities,  lapsed  intelligence  can  have  been  a  factor.  And 
therefore  I  say,  if  such  a  complex  series  \  can  have  resulted 

*  M.  Fabre,  as  interpreted  by  Sir  John  Lubbock,  "Scientific  Lectures," 
2nd  edit.,  p.  45. 

t  In  further  illustration  of  the  fact  that  purposiveness  and  complex 
adaptation  of  activities  is  no  criterion  of  present  or  past  direction  by  intelli- 
gence, we  may  draw  attention  to  the  action  of  the  leucocytes,  or  white  blood- 
corpuscles.  Metchnikoff  found  that  in  the  water-flea  (Daphnia),  affected  by 
spores  of  Monospora  bicuspidata,  a  kind  of  yeast  which  passes  from  the 
intestinal  canal  into  the  body-cavity,  the  leucocytes  attacked  and  devoured 
the  conidia.  If  a  conidium.  were  too  much  for  one  cell,  a  plasmodium,  or 
compound  giant-cell,  was  formed  to  repel  the  invader.  The  same  thing  occurs 
in  anthrax,  the  bacilli  being  attacked  and  devoured  by  the  leucocytes.  "  If 
we  summarize,"  says  Mr.  Bland  Sutton  ("General  Pathology,"  pp.  J27,  128), 
"  the  story  of  inflammation  as  we  read  it  zoologically,  it  should  be  likened  to 
a  battle.  The  leucocytes  are  the  defending  army,  their  roads  and  lines  of 
communication  the  blood-vessels.  Every  composite  organism  maintains  a 
certain  proportion  of  leucocytes  as  representing  its  standing  army.  When  the 
body  is  invaded  by  bacilli,  bacteria,  micrococci,  chemical  or  other  irritants, 
information  of  the  aggression  is  telegraphed  by  means  of  the  vaso-motor 
nerves,  and  leucocytes  rush  to  the  attack ;  reinforcements  and  recruits  are 
quickly  formed  to  increase  the  standing  army,  sometimes  twenty,  thirty,  or 
forty  times  the  normal  standard.  In  the  conflict,  cells  die  and  often  are 
eaten  by  their  companions;  frequently  the  slaughter  is  so  great  that  the 
tissue  becomes  burdened  by  the  dead  bodies  of  the  soldiers  in  the  form  of 
pus,  the  activity  of  the  cell  being  testified  by  the  fact  that  its  protoplasm 
often  contains  bacilli,  etc.,  in  various  stages  of  destruction.  These  dead  cells, 
like  the  corpses  of  soldiers  who  fall  in  battle,  later  become  hurtful  to  tho 
organism  they  weje  in  their  lifetime  anxious  to  protect  from  harm,  for  they 


44-O  Animal  Life  and  Intelligence. 

from  natural  selection  and  non-intelligent  adaptation,  I 
see  no  a  priori  reason  why  any  instinct,  no  matter  how 
complex,  should  not  have  had  a  like  origin. 

Let  us,  however,  next  consider  whether  Professor  Weis- 
mann's  theory  of  the  origin  of  instincts  necessarily 
altogether  excludes  intelligence  as  a  co-operating  factor. 
The  essential  point  on  which  that  theory  is  absolutely 
insistent  is  that  what  is  handed  on  through  inheritance  is 
an  innate,  and  not  an  individually  acquired,  character.  Now, 
since  intelligent  actions  are  characteristically  individual,  and 
performed  in  special  adaptation  to  special  circumstances, 
it  would  seem,  at  first  sight,  that  the  intelligent  modification 
of  an  instinct  could  not,  on  Professor  Weismann's  view,  be 
handed  on.  Let  us  consider  whether  this  must  be  so. 

Speaking  of  ants  and  bees,  Darwin  pointed  out  that 
their  instincts  could  not  possibly  have  been  acquired  by 
inherited  habit,  since  they  are  performed  by  neuter  insects, 
that  is,  by  undeveloped  females  incapable  of  laying  eggs 
and  continuing  their  race.  For  a  habit  to  pass  into  an 
instinct  by  inheritance,  it  is  obviously  necessary  that  the 
organism  which  performs  the  habitual  actions  should  be 
capable  of  producing  offspring  by  which  these  actions  might 
be  inherited.  But  in  this  case  the  parental  forms  do  not 
possess  these  instincts,  while  the  neuter  insects  which  do 
possess  them  are  sterile. 

And  how  does  Mr.  Darwin  meet  this  difficulty  ?  "  It  is 
lessened,  or,  as  I  believe,  disappears,"  he  says,*  "  when  it 
is  remembered  that  selection  may  be  applied  to  the  family 

are  fertile  sources  of  septicaemia  and  pyaemia — the  pestilence  and  scourge  so 
much  dreaded  by  operative  surgeons."  Now,  if  the  leucocytes  were  separate 
organisms,  whose  habits  were  being  described,  some  might  suppose  that  they 
were  actuated  by  intelligence,  individual  or  inherited.  But  in  this  case  the 
activities  are  purely  physiological.  The  marshalling  of  the  cells  during  the 
growth  of  tissue  (e.g.  the  antler  of  a  stag  before  described)  is  of  like  import. 
And  Dr.  Verworn  has  shown  that  when  a  (presumably  weak)  electric  current 
is  passed  through  a  drop  of  water  containing  protozoa,  they  will,  when  the 
current  is  closefl,  flock  towards  the  negative  pole,  and  when  the  current  is 
opened  will  travel  towards  the  positive  pole.  The  implication  of  all  this  is 
that  vital  phenomena  may  be  intensely  purposive,  and  yet  afford  no  evidence 
or  indication  of  the  present  or  ancestral  play  of  intelligence. 
*  "  Origin  of  Species,"  p.  230. 


Habit  and  Instinct.  441 

as  well  as  to  the  individual.  Breeders  of  cattle  wish  the 
flesh  and  fat  to  be  well  marbled  together ;  an  animal  thus 
characterized  has  been  slaughtered,  but  the  breeder  has 
gone  with  confidence  to  the  same  stock,  and  has  succeeded. 
Such  faith  may  be  placed  in  the  power  of  selection,  that  a 
breed  of  cattle  always  yielding  oxen  with  extraordinarily 
long  horns  could,  it  is  probable,  be  formed  by  carefully 
watching  which  individual  bulls  and  cows,  when  matched, 
produced  oxen  with  the  longest  horns ;  and  yet  no  one  ox 
would  ever  have  propagated  his  kind.  .  .  .  Hence  we  may 
conclude  that  slight  modifications  of  structure  or  of  instinct, 
correlated  with  the  sterile  condition  of  certain  members  of 
the  community,  have  proved  advantageous ;  consequently, 
the  fertile  males  and  females  have  flourished,  and  trans- 
mitted to  their  fertile  offspring  a  tendency  to  produce 
sterile  members  with  the  same  modifications.  This  process 
must  have  been  repeated  many  times,  until  that  prodigious 
amount  of  difference  between  the  fertile  and  sterile  females 
of  the  same  species  has  been  produced  which  we  see  in 
many  social  insects." 

Now  let  us  apply  this  illustration  to  the  case  of  habits 
intelligently  acquired.  Instead  of  the  possession  of  long 
horns,  suppose  the  performance  of  some  habitual  action 
be  observed  in  the  oxen.  Then,  by  carefully  watching 
which  individual  bulls  and  cows,  when  matched,  produced 
oxen  which  performed  this  intelligent  habitual  action,  a 
breed  of  cattle  always  yielding  oxen  which  possessed  this 
habit  might,  on  Darwin's  principles,  "be  produced.  The 
intelligence  of  oxen  might  in  this  way  be  enhanced.  Such 
faith  may  be  placed  in  the  power  of  selection  that  a  breed 
of  cattle  <always  yielding  oxen  of  marked  intelligence 
could,  it  is  possible,  be  formed  by  carefully  watching  which 
individual  bulls  and  cows,  when  matched,  produced  the 
most  intelligent  oxen ;  and  yet  no  ox  would  ever  have 
propagated  its  kind.  Eegarding,  then,  a  nest  of  ants  or 
bees  as  a  social  community,  mutually  dependent  on  each 
other,  and  subject  to  natural  selection,  that  community 
would  best  escape  elimination  in  which  the  queen  produced 


442  Animal  Life  and  Intelligence. 

two  sets  of  offspring — one  set  in  which  the  procreative 
faculty  was  predominant  to  the  partial  exclusion  of  in- 
telligence, and  another  in  which  intelligent  activities  were 
predominant  to  the  exclusion  of  propagation. 

It  is  possible  that  I  have  weakened  my  case  by  intro- 
ducing such  a  difficult  problem  as  the  instincts  of  neuter 
insects.  And  I  would  beg  the  reader  to  remember  that 
this  is  only  incidental.  What  I  wish  to  indicate  is  that 
among  the  many  variations  to  which  organisms  are  subject, 
there  are  variations  in  their  intelligent  activities ;  that 
these  are  of  elimination  value,  those  animals  which  con- 
spicuously possess  them  escaping  elimination  in  its  several 
modes ;  that  those  survivors  which  thus  escape  elimination 
are  likely  to  hand  on,  through  inheritance,  that  intelligence 
which  enabled  them  to  survive ;  that  if,  thoughout  a  series 
of  generations,  such  intelligence  be  applied  to  some  definite 
end,  nervous  channels  will  tend  to  be  definitely  established, 
and  the  intelligent  activity  will  more  and  more  readily 
become  habitual ;  that  eventually,  through  the  lapsing  of 
intelligence,  these  habitual  activities  may  become  so  fixed 
and  stereotyped  as  to  become  instinctive ;  that  intelligence 
has  thus  been  a  factor  in  the  establishment  of  these  in- 
stinctive activities ;  that  throughout  the  sequence  there  is 
no  inheritance  of  anything  individually  acquired,  the  in- 
telligent variations  being  throughout  of  germinal  origin ; 
and  that,  therefore,  in  the  origin  of  instincts,  the  co-opera- 
tion of  intelligence  and  the  lapsing  of  intelligence  are  not 
excluded  on  the  principles  advocated  by  Professor  Weismann. 

What,  then,  is  excluded?  Anjr  individually  acquired 
increment,  either  in  the  intelligence  displayed  or  the  stereo- 
typing process.  The  subject  of  instinct  and  of  animal 
intelligence  has  not  at  present  been  considered  at  any 
great  length  by  Professor  Weismann,  but,  judging  by  the 
general  tenor  of  his  writings,  I  take  it  that  what  he 
demands  is  definite  proof  that  such  individually  acquired 
increment  is  actually  inherited. 

As  before  indicated  in  the  chapter  on  "Heredity," 
such  proof  it  is,  from  the  nature  of  the  case,  almost  im- 


Habit  and  Instinct.  443 

possible  to  produce.  Suppose  that  we  find  evidence  of  a 
gradually  increasing  application  of  intelligence  to  some 
important  life-activity,  or  a  more  and  more  defined  stereo- 
typing of  some  incompletely  habitual  or  instinctive  action ; 
how  are  we  to  prove  that  the  increment  in  either  case  is 
due  to  the  inheritance  of  individual  acquisitions,  not  to  the 
selection  of  favourable  innate  (that  is  to  say,  germinal) 
variations  ?  Such  a  hopeless  task  may  at  once  be 
abandoned. 

Are  we,  then,  to  leave  the  question  as  insoluble?  I 
think  not.  It  is  still  open  to  us  to  consider  whether  there 
are  any  cases  in  which  the  inheritance  of  acquired  modifica- 
tions is  a  more  probable  hypothesis  than  the  selection  of 
favourable  germinal  variations.  Now,  the  acquisition  of 
an  instinctive  dread  of  man,  and  the  loss  of  this  instinctive 
timidity  under  domestication,  seem  to  be  of  this  kind. 
And  yet  I  doubt  whether  the  evidence  on  this  head  is  con- 
vincing. For  the  loss  of  instinctive  timidity,  Professor 
Weismann  may  invoke  the  aid  of  panmixia.  But  if  there 
is  truth  in  what  I  have  already  urged  on  this  head,  pan- 
mixia will  not  adequately  account  for  the  facts.  On  the 
other  hand,  he  may  contend  that  the  instinctive  dread  is 
not  due  to  the  inheritance  of  individually  acquired  ex- 
perience, but  to  the  selection  of  the  wilder  birds  and 
animals  through  the  persistent  elimination  of  those  which 
are  tame.  And  in  support  of  this  view,  he  may  quote 
Darwin  himself,  who  says,*  "It  is  surprising,  considering 
the  degree  of  persecution  which  they  have  occasionally 
suffered  during  the  last  one  or  two  centuries,  that  the 
birds  of  the  Falklands  and  Galapagos  have  not  become 
wilder ;  it  shows  that  the  fear  of  man  is  not  soon  acquired." 
It  is  questionable,  however,  whether  this  persecution, 
admittedly  occasional,  can  have  much  elimination  value. 
There  is,  however,  the  element  of  imitation  and  instruction 
to  be  taken  into  account,  and  the  difficulty  of  proving  that 
the  timidity  is  really  instinctive.  It  has  frequently  been 
observed  that  birds  become,  after  a  while,  quite  fearless  of 

*  See  Appendix  to  Mr.  Romanes's  "Mental  Evolution  in  Animals,"  p.  361. 


444  Animal  Life  and  Intelligence. 

trains.  Here  elimination  is  practically  excluded ;  but  it 
has  to  be  proved  that  this  fearlessness  is  truly  instinctive. 
Professor  Eimer  says,*  "In  my  garden  every  sparrow  and 
every  crow  know  me  from  afar  because  I  persecute  these 
birds.  Once,  in  the  presence  of  a  friend,  I  shot  a  crow 
from  the  roof  of  my  house,  while  the  pigeons  and  starlings 
on  the  same  roof,  to  the  great  astonishment  of  my  friend, 
to  whom  I  had  predicted  it,  remained  perfectly  quiet. 
They  had  learned  by  frequent  experience  at  what  my  gun 
was  aimed,  and  knew  that  it  did  not  threaten  them." 
There  is  nothing  in  this  'interesting  observation,  however, 
to  show  that  what  the  pigeons  had  learnt  had,  by  inherited 
experience,  become  instinctive.  And  Professor  Weismann 
will  not,  in  all  probability,  be  prepared  to  accept  as  a 
logical  inference  "  that  this  instinct  of  fear,  because  it  can 
be  dispelled  by  experience,  must  be  founded  on  inherited, 
acquired  experience."  t 

Fully  admitting,  then,  that  this  is  a  matter  of  relative 
probability,  and  that  the  observations  and  inferences  in 
this  matter  are  not  by  themselves  convincing,  I  still  think 
that  the  balance  of  probability  is  here  on"  the  side  of  some 
inheritance  of  experience.  Take  next  such  an  instinctive 
habit  as  that  which  dogs  display  of  turning  round  in  a 
narrow  circle  ere  they  lie  down.  In  its  origin  the  instinct 
probably  arose  with  the  object  of  preparing  a  couch  in  the 
long  grass.  Now,  is  this  habit  of  elimination  value  ?  Can 
we  suppose  that  it  arose  through  the  elimination  of  those 
ancestral  animals  which  failed  to  perform  this  habit  ?  I 
find  it  difficult  to  accept  this  view,  though  it  is  just  possible 
that  the  animals  which  did  this  thereby  escaped  the 
observation  of  their  enemies.  It  is  also  possible  that  this 
originally  was  a  merely  purposeless  habit,  a  strange  trick 
of  manner,  which  has  been  inherited,  and  rendered  constant 
and  fixed.  Here  again,  however,  I  think  the  balance  of 
probability  is  that  the  habit  was  intelligently  acquired  and 
inherited. 

I  have  before  drawn  attention  to  the  more  or  less  in- 

*  "  Organic  Evolution,"  p.  227.  t  Ibid.  p.  228. 


Habit  and  Instinct.  445 

completely  instinctive  avoidance,  by  birds  and  lizards,  of 
insects  with  warning  coloration.  That  the  avoidance  is 
not  perfectly  instinctive  is  shown  by  the  fact  that  young 
birds  sometimes  taste  these  caterpillars  or  insects.  But 
a  very  small  basis  of  experience,  often  a  single  case,  is 
sufficient  to  establish  the  association.  And  in  young 
chicks  the  avoidance  of  bees  and  wasps  seems  to  be  perfectly 
instinctive.  The  effects  on  the  young  birds,  however,  can 
hardly  be  of  elimination  value.  Mr.  Poulton  offered  un- 
palatable insects  "to  animals  from  which  all  other  food 
was  withheld.  Under  these  circumstances,  the  insects 
were  eaten,  although  often  after  many  attempts,  and 
evidently  with  the  most  intense  disgust."  *  I  have  caused 
bees  to  sting  young  chickens ;  the  result  was  extreme  dis- 
comfort, but  in  no  cases  permanent  injury  or  death.  If, 
then,  the  instinct  is  not  of  elimination  value,  that  is  to  say, 
not  such  as  to  save  the  possessors  from  elimination,  how 
can  it  have  been  established  by  natural  selection  ?  And  if 
not  due  to  natural  selection,  to  what  can  it  be  due,  save 
inherited  antipathy  ? 

Natural  selection  is  such  a  far-reaching  and  ubiquitous 
factor  in  organic  evolution,  that  it  is  not  likely  that  many 
cases  can  be  found  in  which  the  play  of  elimination  can  be 
rigidly  excluded.  But  there  are  not  a  few  in  which  elimina- 
tion does  not  appear  to  be  the  most  important  factor.  Mr. 
G.  L.  Grant  has  recently  observed  that  the  sparrows  near 
Auckland,  New  Zealand,  have  taken  to  burrowing  holes  in 
sand-cliffs,  like  the  sand-martin.  The  cliff-swallow  of  the 
Eastern  United  States  has  almost  ceased  to  build  nests  in 
the  cliffs,  like  its  progenitors,  and  now  avails  itself  of  the 
protection  afforded  by  the  eaves  of  houses.  The  surviving 
beavers  in  Europe  are  said  to  have  abandoned  the  instinct 
of  building  huts  and  dams.  The  race  being  no  longer 
sufficiently  numerous  to  live  in  communities,  the  survivors 
live  in  deep  burrows.  In  Russian  Lapland,  under  the 
persecution  of  hunters,  the  reindeer  are  reported  to  be 
abandoning  the  tundras,  or  open  lichen-covered  tracts,  for 

*  "  Colours  of  Animals,"  p.  180. 


446  Animal  Life  and  Intelligence. 

the  forests.  The  kea  (Nestor  notabilis),  a  brush-tongued 
parrot  of  New  Zealand,  which  normally  feeds  on  honey, 
fruits,  and  berries,  has,  since  the  introduction  of  sheep, 
taken  to  a  carnivorous  diet.  It  is  said  to  have  begun  by 
pecking  at  the  sheep-skins  hung  out  to  dry ;  subsequently 
it  began  to  attack  living  sheep ;  and  now  it  has  learnt  to 
tear  its  way  down  to  the  fat  which  surrounds  the  kidneys. 
This  habit,  far  from  being  the  result  of  elimination,  is 
rapidly  leading  to  the  elimination  of  the  bird  that  has  so 
strangely  adopted  it. 

Now,  although  in  these  cases  elimination  has,  I 
think,  been  a  quite  subordinate  factor,  I  do  not  adduce 
them  as  convincing  evidence  that  acquired  habits  are 
hereditary.  Instruction  and  imitation  in  each  successive 
generation  may  well  have  come  into  play.  There  is  no 
proof  that  they  are  even  incompletely  instinctive.  But  I 
think  that  these  are  the  kinds  of  activities,  renewed  and 
careful  observations  and,  if  possible,  experiments  on  which, 
may  lead  to  more  decisive  results.  It  would  probably  not 
be  difficult  to  ascertain  how  far  the  carnivorous  habit  of 
the  kea  has  become  hereditary,  and  how  far  it  is  performed 
in  the  absence  of  instruction  and  without  the  possibility  of 
imitation. 

I  confess  that  when  I  look  round  upon  the  varied  habits 
of  birds  and  mammals,  when  I  see  the  frigate  bird  robbing 
the  fish-hawk  of  the  prey  that  it  has  captured  from  the  sea, 
the  bald-headed  chimpanzee  adopting  a  diet  of  small  birds, 
a  Semnopithecus  in  the  Mergui  Archipelago  eating  Crustacea 
and  mollusca,  and  the  koypu,  a  rodent,  living  on  shell- 
fish; when  I  consider  the  divergence  of  habits  in  almost 
every  group  of  organisms,  the  ground-pigeons,  rock-pigeons, 
and  wood-pigeons,  seed-eating  pigeons  and  fruit-eating 
pigeons  ;  the  carrion-eating,  insect-eating,  and  fruit-eating 
crows  ;  the  aquatic  and  terrestrial  kingfishers,  some  living 
on  fish,  some  on  insects,  some  on  reptiles  ;  *  the  divergent 
habits  of  the  ring-ousel  and  the  water-ousel ;  and  the 
peculiar  habits  of  blood-sucking  bats ; — when  I  see  these 

*  Wallace's  "  Darwinism,"  p.  109. 


Habit  and  Instinct.  447 

and  a  thousand  other  modifications  and  divergences  of 
habit,  I  question  whether  the  theory  that  they  have  all 
arisen  through  the  elimination  of  those  forms  which  failed 
to  possess  them  may  not  be  pushed  too  far  ;  I  am  inclined 
to  believe  that  the  inheritance  of  acquired  modifications 
has  been  a  co-operating  factor.  It  is  not  enough  to  say 
that  these  habits  are  all  useful  to  their  several  possessors. 
It  has  to  be  shown  that  they  are  of  elimination  value — that 
their  possession  or  non-possession  has  made  all  the  differ- 
ence between  survival  and  elimination. 

On  the  whole,  then,  as  the  result  of  a  careful  considera- 
tion of  the  subject  of  instinctive  and  habitual  activities, 
and  in  accordance  with  my  general  view  of  organic  evolu- 
tion as  set  forth  in  previous  chapters,  I  am  disposed  to 
accept  the  inheritance  of  individually  acquired  modifications 
of  habit  as  a  working  hypothesis.  I  do  not  think  that 
absolutely  convincing  evidence  thereof  can  at  present  be 
produced.  But  to  the  best  of  my  judgment,  the  probabili- 
ties are  in  favour  of  the  inheritance  of  modifications  of 
existing  activities,  due  to  intelligence,  instruction,  and 
imitation ;  always  provided  that  the  exercise  of  these 
modified  activities  is  sufficiently  frequent  and  definite  to 
give  rise  to  habits  in  the  individual. 

I  recognize  three  factors  in  the  origin  of  instinctive 
activities — 

1.  Elimination  through  natural  selection. 

2.  Selection  through  preferential  mating. 

3.  The  inheritance  of  individually  acquired  modifica- 
tions. 

Of  these  I  consider  the  first  quite  incontrovertible  ;  the 
second  as  highly  probable  ;  and  the  third  as  probable  in  a 
less  degree.  In  all  three,  intelligence  may  or  may  not  have 
been  a  factor.  Some  of  the  habits  which  have  survived 
elimination  under  the  first  factor  may  have  been  originally 
intelligent,  some  of  them  from  the  first  unintelligent. 
Some  of  the  love-antics  (so  called),  which,  through  their 
tendency  to  excite  sexual  appetence  in  the  female,  have 
been  selected  under  the  second  factor,  may  have  had  a 


448  Animal  Life  and  Intelligence. 

basis  in  intelligence  ;  many  of  them  probably  have  not. 
And  though  the  great  majority  of  individually  acquired 
modifications  of  habits  have  owed  their  origin  to  intelligent 
direction,  still  it  is  conceivable  that  some  of  them  have 
not.  An  animal  may  have  been  forced  by  circumstances  to 
modify  its  habits,  without  any  exercise  of  intelligence  ;  and 
this  modification,  forced,  through  changed  conditions,  upon 
all  the  members  of  a  species,  may,  through  inheritance, 
have  passed  into  the  stereotyped  condition  of  an  instinct. 
Under  each  factor,  then,  we  have  two  several  categories. 

1    Elimination  .  .  \  °'  of  unintelligent  activities. 

I  6.  of  intelligent  activities 
9    e  i    t-  (  a.  of  unintelligent  activities. 

"I  6.  of  intelligent  activities. 
3.  Inheritance  .  .  /  a'  of  anintelligent  activities. 

\  b.  of  intelligent  activities. 

In  all  cases,  however,  where  intelligence  has  been  a  co- 
operating factor,  this  intelligence  has  lapsed  so  soon  as  the 
activity  became  truly  instinctive. 

From  the  co-operation  of  the  factors  it  is  almost  im- 
possible to  give  examples  which  shall  illustrate  the  exclu- 
sive action  of  any  one.  The  following  table  must  therefore 
be  regarded  as  indicating  the  probable  predominance  of  the 
factor  indicated  :  — 

a.  Caterpillars  spinning  cocoons. 

b.  Instincts  of  social  hymenoptera. 
2    fa.  Drumming  of  snipe. 

I  6.  Procedure  of  Queensland  bower-bird. 
„    fa.  Ants  forming  nests  in  trees  in  flooded  parts  of  Siam. 
\  b.  Instinctive  fear  of  man. 

In  speaking  of  the  instinct  of  caterpillars  spinning 
cocoons  as  unintelligent,  I  am  regarding  the  final  purpose 
of  the  activity.  Intelligence  may  very  possibly  have  come 
into  play  in  modifying  the  details  of  procedure.  In  giving 
the  drumming  of  snipe  as  an  example  of  unintelligent 
activities  furthered  by  selection,  I  am  assuming  that  it  has 
a  sexual  import,  and  that  the  activity  correlated  with  a 
narrowing  of  the  tail-feathers  was  not,  in  its  inception, 
intelligently  performed  with  the  object  of  exciting  sexual 


( 
\ 


Habit  and  Instinct.  449 

appetence  in  the  hen.  The  case  of  the  ants  of  Siam  is 
given  by  Mr.  Bomanes,*  on  the  authority  of  Lonbiere,  who 
says  "that  in  one  part  of  that  kingdom,  which  lies  open  to 
great  inundations,  all  the  ants  made  their  settlements  upon 
trees ;  no  ants'  nests  are  to  be  seen  anywhere  else."  Now, 
this  modification  of  habits  may  have  been  the  result  of 
intelligence  ;  or  it  may  have  been  forced  upon  the  ants  by 
circumstances.  The  floods  drove  them  on  to  the  trees  ; 
the  instinctive  impulse  to  build  a  settlement  was  impera- 
tive ;  hence  the  settlement  had  to  be  formed  on  the  trees, 
because  the  ground  was  flooded.  The  difficulty  of  ascer- 
taining whether  intelligence  has  or  has  not  been  a  factor 
is  simply  part  of  the  inherent  difficulty  of  comparative 
psychology — a  difficulty  on  which  sufficient  stress  has 
already  been  laid  in  an  earlier  chapter. 

The  great  majority  of  the  instinctive  activities  of  animals 
have  arisen  through  a  co-operation  of  the  factors,  and  it  is 
exceedingly  difficult  in  any  individual  case  to  assign  to  the 
factors  their  several  values. 

And  here  we  must  once  more  notice  that  the  separation 
off  of  the  instinctive  activities  from  the  other  activities  of 
animals  is  merely  a  matter  of  convenience  in  classification. 
In  the  living  organism  the  activities — automatic  actions, 
reflex  actions,  incompletely  and  perfectly  established 
instincts,  habits,  and  intelligent  activities — are  unclassified 
and  commingled.  They  are  going  on  at  the  same  time, 
shading  the  one  into  the  other,  untrammelled  by  the  limits 
imposed  by  a  scientific  method  of  treatment. 

Once  more,  too,  we  must  notice  that  the  activities  of 
animals  are  essentially  the  outcome  and  fulfilment  of 
emotional  states.  When  the  emotional  sensibility  is  high, 
the  resulting  activities  are  varied  and  vigorous.  As  we 
have  before  seen,  this  high  state  of  emotional  sensibility  is 
correlated  with  a  highly  charged  and  sensitive  condition  of 
the  organic  explosives  elaborated  by  the  plasmogen  of  the 
cells.  After  repose,  and  at  certain  periodic  times,  this 
state  of  exalted  sensibility  is  apt  to  occur.  It  is  exemplified 

*  "  Mental  Evolution  in  Animals,"  p.  244. 

2G 


45°  Animal  Life  and  Intelligence. 

in  the  so-called  instinct  of  play,  which  manifests  itself  in 
varied  activities  in  the  early  morning,  in  early  life,  and 
in  the  returning  warmth  of  spring — at  such  times,  in  fact, 
as  the  life-tide  is  in  full  flood. 

But  perhaps  the  activities  which  result  from  a  highly 
wrought  state  of  sensibility  are  best  seen  at  the  periodic 
return  of  sexual  appetence  or  impulse  in  animals  of  various 
grades  of  life  and  intelligence.    Many  organisms,  at  certain 
periods  of  the  year,  and  in  presence  of  their  mates,  are 
thrown  into  a  perfect  frenzy  of  sexual   appetence.     The 
love-antics  of  birds  have  been  so  frequently  described  that 
I  will  merely  quote  from  Darwin  *  Mr.  Strange's  account 
of  the  satin  bower-bird :    "At  times  the  male  will  chase 
the  female  all  over  the  aviary,  then  go  to  the  bower,  pick 
up  a  gay  feather  or  a  large  leaf,  utter  a  curious  kind  of 
note,  set  all  his  feathers  erect,  run  round  the  bower,  and 
become  so   excited  that   his   eyes   appear   ready  to  start 
from  his  head ;  he  continues  opening  first  one  wing,  and 
then  the  other,  uttering  a  low,  whistling  note,  and,  like  the 
domestic  cock,  seems  to  be  picking  up  something  from  the 
ground,  until  at  last  the  female  goes  gently  towards  him." 
Instances  might  be  quoted  from  almost  all  classes  of  the 
animal  kingdom.      Many   fish  display  "  love-antics,"   for 
example,    the   gay-suited,   three-spine   stickleback,   whose 
excitement  is  apparently  intense.      Newts  display  similar 
activities.     Even  the  lowly  snail  makes  play  with  its  love- 
darts  (spiculte  amoris),  practical  tangible  darts  of  glistening 
carbonate  of  lime.     Mr.  George  W.  Peckham  has  recently 
described!  the   extraordinary  "love-dance"   of  a   spider 
(Saitis  pulex}.     "  On  May  24  we  found  a  mature  female, 
and  placed  her  in  one  of  the  larger  boxes ;  and  the  next 
day  we  put  a  male  in  with  her.     He  saw  her  as  she  stood 
perfectly  still,  twelve  inches  away;  the  glance  seemed  to 
excite  him,  and  he  at  once  moved  towards  her ;  when  some 
four  inches  from  her  he  stood  still,  and  then  began  the 

*  "Descent  of  Man,"  pt.  ii.  chap.  xiii. 

t  George  W.  and  Elizabeth  G.   Peckham,  "Occasional  Papers  of  the 
Natural  History  of  Wisconsin,"  vol.  i.  (1889),  p.  37. 


Habit  and  Instinct.  45  [ 

most  remarkable  performances  that  an  amorous  male  could 
offer  to  an  admiring  female.  She  eyed  him  eagerly, 
changing  her  position  from  time  to  time,  so  that  he  might 
be  always  in  view.  He,  raising  his  whole  body  on  one 
side  by  straightening  out  the  legs,  and  lowering  it  on  the 
other  by  folding  the  first  two  pairs  of  legs  up  and  under, 
leaned  so  far  over  as  to  be  in  danger  of  losing  his  balance, 
which  he  only  maintained  by  sidling  rapidly  towards  the 
lowered  side.  The  palpus,  too,  on  this  side  was  turned 
back  to  correspond  to  the  direction  of  the  legs  nearest  it. 
He  moved  in  a  semicircle  for  about  two  inches,  and  then 
instantly  reversed  the  position  of  the  legs,  and  circled  in 
the  opposite  direction,  gradually  approaching  nearer  and 
nearer  to  the  female.  Now  she  dashes  towards  him,  while 
he,  raising  his  first  pair  of  legs,  extends  them  upward  and 
forward  as  if  to  hold  her  off,  but  withal  slowly  retreats. 
Again  and  again  he  circles  from  side  to  side,  she  gazing 
towards  him  in  a  softer  mood,  evidently  admiring  the  grace 
of  his  antics.  This  is  repeated  until  we  have  counted  a 
hundred  and  eleven  circles  made  by  the  ardent  little  male. 
Now  he  approaches  nearer  and  nearer,  and  when  almost 
within  reach  whirls  madly  around  and  around  her,  she 
joining  and  whirling  with  him  in  a  giddy  maze.  Again  he 
falls  back  and  resumes  his  semicircular  motions,  with  his 
body  tilted  over  ;  she,  all  excitement,  lowers  her  head  and 
raises  her  body,  so  that  it  is  almost  vertical ;  both  draw 
nearer ;  she  moves  slowly  under  him,  he  crawling  over  her 
head,  and  the  mating  is  accomplished." 

It  can  scarcely  be  doubted  that  such  antics,  performed 
in  presence  of  the  female  and  suggested  at  sight  of  her, 
serve  to  excite  in  the  mate  sexual  appetence.  If  so,  it  can, 
further,  scarcely  be  doubted  that  there  are  degrees  of  such 
excitement,  that  certain  antics  excite  sexual  appetence  in 
the  female  less  fully  or  less  rapidly  than  others ;  yet  others, 
perhaps,  not  at  all.  If  so,  again,  it  can  hardly  be  ques- 
tioned that  those  antics  which  excite  most  fully  or  most 
rapidly  sexual  appetence  in  the  female  will  be  perpetuated 
through  the  selection  of  the  male  which  performs  them. 


45 2  Animal  Life  and  Intelligence. 

This  is  sexual  selection  through  preferential  mating.  And, 
I  think,  the  importance  of  these  activities,  their  wide  range, 
and  their  perfectly,  or  at  any  rate  incompletely  instinctive 
nature,  justifies  me  in  emphasizing  this  factor  in  the  origin 
of  instinctive  activities.  It  has  hitherto,  I  think,  not 
received  the  attention  it  deserves  in  discussions  of  instinct. 

A  few  more  words  may  here  be  added  to  what  has 
already  been  said  on  the  influence  of  intelligence  on 
instinct.  The  influence  may  be  twofold — it  may  aid  in 
making  or  in  unmaking  instincts.  We  have  seen  that 
instincts  may  be  modified  through  intelligent  adaptation. 
A  little  dose  of  judgment,  as  Huber  phrased  it,  often  comes 
into  play.  The  cell-building  instinct  of  bees  is  one  which 
is  remarkably  stereotyped ;  and  yet  it  may  be  modified  in 
intelligent  ways  to  meet  special  circumstances.  When, 
for  example,  honey-bees  were  forced  to  build  their  comb 
on  the  curve,  the  cells  on  the  convex  side  were  made  of  a 
larger  size  than  usual,  while  those  on  the  concave  side 
were  smaller  than  usual.  Huber  constrained  his  bees  to 
construct  their  combs  from  below  upwards,  and  also 
horizontally,  and  thus  to  deviate  from  their  normal  mode 
of  building.  The  nest-construction  of  birds,  again,  may 
be  modified  in  accordance  with  special  circumstances. 
And,  perhaps,  it  is  scarcely  too  much  to  say  that,  when- 
ever intelligence  comes  on  the  scene,  it  may  be  employed 
in  modifying  instinctive  activities  and  giving  them  special 
direction. 

Now,  suppose  the  modifications  are  of  various  kinds 
and  in  various  directions,  and  that,  associated  with  the 
instinctive  activity,  a  tendency  to  modify  it  indefinitely  be 
inherited.  Under  such  circumstances  intelligence  would 
have  a  tendency  to  break  up  and  render  plastic  a  previously 
stereotyped  instinct.  For  the  instinctive  character  of  the 
activities  is  maintained  through  the  constancy  and  uni- 
formity of  their  performance.  But  if  the  normal  activities 
were  thus  caused  to  vary  in  different  directions  in  different 
individuals,  the  offspring  arising  from  the  union  of  these 
differing  individuals  would  not  inherit  the  instinct  in  the 


Habit  and  Instinct.  453 

same  purity.  The  instincts  would  be  imperfect,  and  there 
would  be  an  inherited  tendency  to  vary.  And  this,  if  con- 
tinued, would  tend  to  convert  what  had  been  a  stereotyped 
instinct  into  innate  capacity ;  that  is,  a  general  tendency 
to  certain  activities  (mental  or  bodily),  the  exact  form  and 
direction  of  which  is  not  fixed,  until  by  training,  from 
imitation  or  through  the  guidance  of  individual  intelligence, 
it  became  habitual.  Thus  it  may  be  that  it  has  come 
about  that  man,  with  his  enormous  store  of  innate  capacity, 
has  so  small  a  number  of  stereotyped  instincts. 

But  while  intelligence,  displayed  under  its  higher  form 
of  originality,  may,  in  certain  cases,  lead  to  all-round 
variation,  tending  to  undermine  instinct  and  render  it  less 
stereotyped,  intelligence,  under  its  lower  form  of  imitation, 
has  the  opposite  tendency.  For  young  animals  are  more 
likely  to  imitate  the  habits  of  their  own  species  than  the 
foreign  habits  of  other  species,  and  such  imitation  would 
therefore  tend  towards  uniformity. 

Imitation  is  probably  a  by  no  means  unimportant  factor 
in  the  development  of  habits  and  instincts.  Mr.  A.  E. 
Wallace,  in  his  "  Contributions  to  the  Theory  of  Natural 
Selection,"  contends  that  the  nest-building  habit  in  birds 
is,  to  a  large  extent,  kept  constant  by  imitation.  The 
instinctive  motive  is  there,  but  the  stereotyped  form  is 
maintained  through  imitation  of  the  structure  of  the  nest 
in  which  the  builders  were  themselves  reared.  Mr.  Weir, 
however,  writing  to  Mr.  Darwin,  in  1868,  says  in  a  letter, 
which  Mr.  Eomanes  quotes,*  "  The  more  I  reflect  on  Mr. 
Wallace's  theory,  that  birds  learn  to  make  their  nests 
because  they  have  themselves  been  reared  in  one,  the  less 
inclined  do  I  feel  to  agree  with  him.  ...  It  is  usual  with 
canary-fanciers  to  take  out  the  nest  constructed  by  the 
parent  birds,  and  to  place  a  felt  nest  in  its  place,  and, 
when  the  young  are  hatched  and  old  enough  to  be  handled, 
to  place  a  second  clean  nest,  also  of  felt,  in  the  box,  remov- 
ing the  other.  This  is  done  to  prevent  acari.  But  I  never 
knew  that  canaries  so  reared  failed  to  make  a  nest  when 

*  "Mental  Evolution  in  Animals,"  p.  226. 


454  Animal  Life  and  Intelligence. 

the  breeding-time  arrived.  I  have,  on  the  other  hand, 
marvelled  to  see  how  like  a  wild  bird's  the  nests  are  con- 
structed. It  is  customary  to  supply  them  with  a  small  set 
of  materials,  such  as  moss  and  hair.  They  use  the  moss 
for  the  foundation,  and  line  with  the  finer  materials,  just 
as  a  wild  goldfinch  would  do,  although,  making  it  in  a 
box,  the  hair  alone  would  be  sufficient  for  the  purpose.  I 
feel  convinced  nest-building  is  a  true  instinct."  On  the 
other  hand,  Mr.  Charles  Dixon,  quoted*  in  Mr.  Wallace's 
"Darwinism,"  speaking  of  chaffinches  which  were  taken  to 
New  Zealand  and  turned  out  there,  says,  "  The  cup  of  the 
nest  is  small,  loosely  put  together,  apparently  lined  with 
feathers,  and  the  walls  of  the  structure  are  prolonged  for 
about  eighteen  inches,  and  hang  loosely  down  the  side  of 
the  supporting  branch.  The  whole  structure  bears  some 
resemblance  to  the  nests  of  the  hang-birds  (Icteridce),  with 
the  exception  that  the  cavity  is  at  the  top.  Clearly  these 
New  Zealand  chaffinches  were  at  a  loss  for  a  design  when 
fabricating  their  nest.  They  had  no  standard  to  work  by, 
no  nests  of  their  own  kind  to  copy,  no  older  birds  to  give 
them  any  instruction,  and  the  result  is  the  abnormal 
structure  I  have  just  described." 

There  is  more  evidence  in  favour  of  the  view  that  the 
song  of  birds  is,  in  part  at  least,  imitative.  That  it  has  an 
innate  basis  is  certain ;  and  that  it  may  be  truly  instinctive 
is  shown  by  Mr.  Couch's  observation  of  a  goldfinch  which 
had  never  heard  the  song  of  its  own  species,  but  which 
sang  the  goldfinch-song,  though  tentatively  and  imperfectly. 
On  the  other  hand,  imitation  is  undoubtedly  a  factor.  The 
Hon.  Daines  Barrington  says  (1773),  "I  have  educated 
nestling  linnets  under  the  three  best  singing  larks — the 
skylark,  woodlark,  and  titlark — every  one  of  which,  instead 
of  the  linnet's  song,  adhered  entirely  to  that  of  their 
respective  instructors.  When  the  note  of  the  titlark  linnet 
was  thoroughly  fixed,  I  hung  the  bird  in  a  room  with  two 
common  linnets  for  a  quarter  of  a  year.  They  were  in  full 
song,  but  the  titlark  linnet  adhered  steadfastly  to  that  of 

*  "Darwinism,"  p.  76,  from  Nature,  vol.  xxxi.  p.  533. 


Habit  and  Instinct.  455 

the  titlark."  Mr.  Wallace,  who  quotes  this,  adds,*  "  For 
young  birds  to  acquire  a  new  song  correctly,  they  must  be 
taken  out  of  hearing  of  their  parents  very  soon,  for  in  the 
first  three  or  four  days  they  have  already  acquired  some 
knowledge  of  the  parent's  notes,  which  they  afterwards 
imitate."  Bureau  de  la  Malle,  as  quoted  by  Mr.  Bomanes,f 
describes  how  he  taught  a  starling  the  "  Marseillaise,"  and 
from  this  bird  all  the  other  starlings  in  a  canton  to  which 
he  took  it  are  stated  to  have  learned  the  air  ! 

That  dogs,  monkeys,  and  other  mammalia  have  powers 
of  imitation  needs  no  illustration.  And  when  we  remember 
that  it  is  only  the  imitation  of  strange  and  unusual  actions 
that  arrests  our  attention,  while  the  imitation  of  normal 
activities  is  likely  to  pass  unnoticed,  we  may,  I  think,  fairly 
surmise  that  imitation  is  by  no  means  an  unimportant 
factor  in  the  acquisition  and  development  of  habits.  And 
where  the  young  animal  is  surrounded  during  the  early 
plastic  and  imitative  period  of  life  by  its  own  kith  and  kin, 
imitation  will  undoubtedly  have  a  conservative  tendency. 

The  education  of  young  animals  by  their  parents  has 
also  a  conservative  tendency.  Mr.  Spalding's  observations 
show  that  the  flight  of  birds  is  instinctive ;  but  the  parent 
birds  normally  aid  the  development  of  the  instincts  by 
instruction.  Ants,  as  we  have  seen,  are  instructed  in  the 
business  of  ant-life.  Dogs  and  cats  train  their  young. 
And  Darwin  tells  us,  on  the  authority  of  Youatt,J  that 
lambs  turned  out  without  their  mothers  are  very  liable  to 
eat  poisonous  herbs. 

We  may  say,  then,  with  regard  to  the  influence  of 
intelligence  on  instinctive  activities,  that  it  may  lead  them 
to  vary  along  certain  definite  lines  of  increased  adaptation  ; 
that  it  may,  in  some  cases,  lead  them  to  vary  along  divergent 
lines,  and  hence  tend  to  render  stereotyped  instincts  more 
plastic ;  and  that,  through  imitation  and  instruction,  it 
may  tend  to  render  instinctive  habits  more  uniform  in  a 
community,  and  hence,  if  the  habits  are  tending  to  vary 

*  "Contributions,"  etc., p.  222. 
t  "Mental  Evolution  in  Animals,"  p.  222.  $  "On  Sheep,"  p.  404. 


456  Animal  Life  and  Intelligence. 

under  changed  circumstances  in  a  given  direction,  may 
tend  to  draw  the  habits  of  all  the  members  of  the  com- 
munity in  that  given  direction. 

And  with  regard  to  the  more  general  question  of  the 
variation  of  habits  and  instincts,  we  may  say  that,  in 
addition  to  those  variations  in  the  origin  and  direction  of 
which  intelligence  is  a  factor,  there  are  other  variations 
which  take  their  origin  without  the  influence  of  intelligence 
under  the  stress  of  changing  circumstances,  and  yet  others 
which  may  arise  as  we  say  " fortuitively  "  or  "by  chance," 
that  is,  from  some  cause  or  causes  whereof  we  are  at 
present  ignorant,  and  which  do  not  appear  to  be  evoked 
directly  by  the  stress  of  environing  circumstances. 

Granting,  however,  the  existence  of  these  variations  in 
whatsoever  way  arising,  and  granting  the  influence  of 
natural  selection,  of  sexual  selection,  and  perhaps  of  the 
inheritance  of  individually  acquired  modifications,  those 
variations  which  are  for  the  good  of  the  race  or  species  in 
which  they  occur  will  have  a  tendency  to  be  perpetuated, 
while  those  which  are  detrimental  will  be  weeded  out  and 
will  tend  to  disappear. 

Passing  on  now  to  consider  the  characteristics  of  those 
activities  which  we  term  "intelligent,"  we  may  first  notice 
what  Mr.  Charles  Mercier,  in  "  The  Nervous  System  and 
the  Mind,"  calls  the  four  criteria  of  intelligence.  Intelli- 
gence is  manifested,  he  says,  first,  in  the  novelty  of  the 
adjustments  to  external  circumstances  ;  secondly,  in  the 
complexity;  thirdly,  in  the  precision;  and  fourthly,  in 
dealing  with  the  circumstances  in  such  a  way  as  to  extract 
from  them  the  maximum  of  benefit. 

Now,  I  think  it  is  clear  that,  when  it  is  our  object  to 
distinguish  intelligent  from  instinctive  activities,  the  pre- 
cision of  the  adjustment  cannot  be  regarded  as  a  criterion 
of  intelligence.  Many  instinctive  acts  are  wonderfully  pre- 
cise. The  sphex  is  said  to  stab  the  spider  it  desires  to 
paralyze  with  unerring  aim  in  the  central  nerve-ganglion. 
Other  species,  which  paralyze  crickets  and  caterpillars, 
pierce  them  in  three  and  nine  places  respectively,  according 


Habit  and  Instinct.  457 

to  the  number  of  the  ganglia.  And  yet  this  seems  to  be  a 
purely  instinctive  action.  So,  too,  to  take  but  one  more 
example,  there  is  surely  no  lack  of  precision  in  the  cell- 
making  instinct  of  bees.  We  may  say,  then,  that,  grant- 
ing that  an  action  is  intelligent,  the  precision  of  the 
adjustment  is  a  criterion  of  the  level  of  intelligence;  but 
that,  since  there  may  be  instinctive  actions  of  wonderful 
precision,  this  criterion  is  not  distinctive  of  intelligence. 
Nay,  more,  there  are  many  reflex  actions  of  marvellous 
precision  and  accuracy  of  adjustment ;  and  there  can  be 
no  question  of  intelligence,  individual  or  ancestral,  in 
many  of  these. 

Nor  can  we  regard  prevision  (which  is  sometimes 
advanced  as  a  criterion  of  intelligence)  as  specially  dis- 
tinctive of  intelligent  acts  regarded  objectively  in  the 
study  of  the  activities  of  animals.  For,  as  we  have 
already  seen,  there  are  many  instincts  which  display  an 
astonishing  amount  of  what  I  ventured  to  term  "  blind  pre- 
vision " — instance  the  instinctive  regard  for  the  welfare  of 
unborn  offspring,  and  the  instinctive  preparation  for  an 
unknown  future  state  in  the  case  of  insect  larvae. 

Nor,  again,  is  the  complexity  of  the  adjustment  distinc- 
tive of  intelligence  as  opposed  to  instinct.  The  case  of  the 
sitaris,  before  given,  the  larva  of  which  attaches  itself  to  a 
male  bee,  passes  on  to  the  female,  springs  upon  the  eggs 
she  lays,  eats  first  the  egg  and  then  the  store  of  honey, — 
this  case,  I  say,  affords  us  a  series  of  sufficiently  marked 
complexity.  This  instinct,  the  paralyzing,  but  not  killing 
outright,  of  prey  by  the  sphex ;  the  marvellous  economy  of 
wax  in  the  cell-building  of  the  honey-bee ;  the  affixing  to 
their  body,  by  crabs,  of  seaweed  (Stenorhynchus) ,  of  ascidians 
(an  Australian  Dromia},  of  sponge  (Dromia  vulgaris),  of  the 
cloaklet  anemone  (Pagurus  prideauxii} ;  and  other  cases 
too  numerous  for  citation; — these  show,  too,  that  the 
circumstances  may  be  dealt  with  in  such  a  way  as  to 
extract  from  them  the  maximum  of  benefit,  probably  with- 
out intelligence.  It  would  be  quite  impossible  intelli- 
gently to  improve  upon  the  manner  of  dealing  with  the 


4.S&  Animal  Life  and  Intelligence. 

circumstances  displayed  in  many  instinctive  activities, 
even  those  which  we  have  reason  to  believe  were  evolved 
without  the  co-operation  of  intelligence. 

There  remain,  therefore,  the  novelty  of  the  adjustment 
and  the  individuality  displayed  in  these  adjustments.  And 
here  we  seem  to  have  the  essential  features  of  intelligent 
activities.  The  ability  to  perform  acts  in  special  adaptation 
to  special  circumstances,  the  power  of  exercising  individual 
choice  between  contradictory  promptings,  and  the  indi- 
viduality or  originality  manifested  in  dealing  with  the 
complex  conditions  of  an  ever-changing  environment, — 
these  seem  to  be  the  distinctive  features  of  intelligence. 
On  the  other  hand,  in  instinctive  actions  there  seems  to  be 
no  choice ;  the  organism  is  impelled  to  their  performance 
through  impulse,  as  by  a  stern  necessity ;  they  are  so  far 
from  novel  that  they  are  performed  by  every  individual  of 
the  species,  and  have  been  so  performed  by  their  ancestors 
for  generations ;  and,  in  performing  the  instinctive  action, 
the  animal  seems  to  have  no  more  individuality  or  originality 
than  a  piece  of  adequately  wound  clockwork. 

It  may  be  said  that,  in  granting  to  animals  a  power  of 
individual  choice,  we  are  attributing  to  them  free-will ;  and 
surely  (it  may  be  added),  after  denying  to  them  reason,  we 
cannot,  in  justice  and  in  logic,  credit  them  with  this,  man's 
choicest  gift.  I  shall  not  here  enter  into  the  free-will  con- 
troversy. I  shall  be  content  with  denning  what  I  mean  by 
saying  that  animals  have  a  power  of  individual  choice. 
Two  weather-cocks  are  placed  on  adjoining  church  pinnacles, 
two  clouds  are  floating  across  the  sky,  two  empty  bottles 
are  drifting  down  a  stream.  None  of  these  has  any  power 
of  individual  choice.  They  are  completely  at  the  mercy  of 
external  circumstances.  On  the  other  hand,  two  dogs  are 
trotting  down  the  road,  and  come  to  a  point  of  divergence  ; 
one  goes  to  the  right  hand,  the  other  to  the  left  hand. 
Here  each  exercises  a  power  of  individual  choice  as  to 
which  way  he  shall  go.  Or,  again,  my  brother  and  I  are 
out  for  a  walk,  and  our  father's  dog  is  with  us.  After  a 
while  we  part,  each  to  proceed  on  his  own  way.  Pincher 


Habit  and  Instinct.  459 

stands  irresolute.  For  a  while  the  impulse  to  follow  me 
and  the  impulse  to  follow  my  brother  are  equal.  Then  the 
former  impulse  prevails,  and  he  bounds  to  my  side.  He 
has  exercised  a  power  of  individual  choice.  If  any  one  likes 
to  call  this  yielding  to  the  stronger  motive  an  exercise  of 
free-will,  I,  for  one,  shall  not  say  him  nay.  What  I  wish 
specially  to  notice  about  it  is  that  we  have  here  a  sign  of 
individuality.  There  is  no  such  individuality  in  inorganic 
clouds  or  empty  bottles.  Choice  is  a  symbol  of  indi- 
viduality ;  and  individuality  is  a  sign  of  intelligence. 

But  though  I  decline  here  to  enter  into  the  free-will 
controversy,  I  may  fairly  be  asked  where  I  place  volition 
in  the  series  between  external  stimulus  and  resulting 
activity;  and  what  I  regard  as  the  concomitant  physio- 
logical manifestation.  I  doubt  whether  I  shall  be  able  to 
say  anything  very  satisfactory  in  answer  to  these  questions. 
I  shall  have  to  content  myself  with  little  more  than  stating 
how  the  problem  presents  itself  to  my  mind. 

I  believe  that  volition  is  intimately  bound  up  and 
associated  with  inhibition.  I  go  so  far  as  to  say  that, 
without  inhibition,  volition  properly  so  called  has  no 
existence.  When  the  series  follows  the  inevitable  sequence  — 

Stimulus  :  perception  :  emotion  :  fulfilment  in  action 

—  the  act  is  involuntary.  And  such  it  must  ever  have  re- 
mained, had  not  inhibition  been  evolved,  had  not  an 
alternative  been  introduced,  thus  —  • 

fu'fiment 


Stimulus  :  perception  :  emotion 

N  inhibition  of  action. 

At  the  point  of  divergence  I  would  place  volition.  Volition 
is  the  faculty  of  the  forked  way.  There  are  two  possibilities 
—  fulfilment  in  action  or  inhibition.  I  can  write  or  I  can 
cease  writing  ;  I  can  strike  or  I  can  forbear.  And  my  poor 
little  wounded  terrier,  whose  gashed  side  I  was  sewing  up, 
clumsily,  perhaps,  but  with  all  the  gentleness  and  tender- 
ness I  could  command,  could  close  his  teeth  on  my  hand 
or  could  restrain  the  action. 

I  have  here,  so  to   speak,  reduced  the  matter  to  its 


460  Animal  Life  and  Intelligence. 

simplest  expression.  It  is  really  more  complex.  For 
volition  involves  an  antagonism  of  motives,  one  or  more 
prompting  to  action,  one  or  more  prompting  to  restraint. 
The  organism  yields  to  the  strongest  prompting,  acts  or 
refrains  from  acting  'according  as  one  motive  or  set  of 
motives  or  the  other  motive  or  set  of  motives  prevails ;  in 
other  words,  according  as  the  stimuli  to  action  or  the  in- 
hibitory stimuli  are  the  more  powerful. 

And  then  we  must  remember  that  the  perceptual . 
volition  of  animals  becomes  in  us  the  conceptual  volition 
of  man.  An  animal  can  choose,  and  is  probably  conscious 
of  choosing.  This  is  its  perceptual  volition.  Man  not 
only  chooses,  and  is  conscious  of  choosing,  but  can  reflect 
upon  his  choice ;  can  see  that,  under  different  circumstances, 
his  choice  would  have  been  different ;  can  even  fancy  that, 
under  the  same  circumstances  (external  and  internal),  his 
choice  might  have  been  different.  This  is  conceptual 
volition.  Just  as  Spinoza  said  that  desire  is  appetence 
with  consciousness  of  self ;  so  may  we  say  that  the  volition 
of  contemplative  man  is  the  volition  of  the  brute  with  con- 
sciousness of  self.  No  animal  has  consciousness  of  self; 
that  is  to  say,  no  animal  can  reflect  on  its  own  conscious 
states,  and  submit  them  to  analysis  with  the  formation  of 
isolates.  Self-consciousness  involves  a  conception  of  self, 
persistent  amid  change,  and  isolable  in  thought  from  its 
states.  It  involves  the  isolation  in  thought  of  phenomena 
not  isolable  in  experience.  We  can  think  about  the  self 
as  distinct  from  its  conscious  states  and  the  bodily  organi- 
zation; but  they  are  no  more  separable  in  experience  than 
the  rose  is  separable  from  its  colour  or  its  scent.  Such 
isolation  is  impossible  to  the  brute.  An  animal  is  con- 
scious of  itself  as  suffering,  but  the  consciousness  is  per- 
ceptual. There  is  no  separation  of  the  self  as  an  entity 
distinct  from  the  suffering  which  is  a  mere  accident  thereof ; 
no  conception  of  a  self  which  may  suffer  or  not  suffer,  may 
act  or  may  not  act,  maybe  connected  with  the  body  or  may 
sever  that  connection.  Just  as  there  is  a  vast  difference 
between  the  perception  of  an  object  as  here  and  not  there, 


Habit  and  Instinct.  461 

of  an  occurrence  as  now  and  not  then,  of  a  touch  as  due 
to  a  solid  body;  and  the  conception  of  space,  time,  and 
causation ;  so  is  there  a  vast  difference  between  a  percep- 
tion of  an  injury  as  happening  to  one's  self,  and  a  con- 
ception of  self  as  the  actual  or  possible  subject  of  painful 
consciousness.  This  difference  is  clearly  seen  by  Mr. 
Mivart,  who  therefore  speaks  of  the  consentience  of  brutes 
as  opposed  to  the  consciousness  of  man.  Consciousness 
he  regards  as  conceptual ;  consentience  as  perceptual.* 
And,  as  before  stated,  I  should  be  disposed  to  accept  his 
nomenclature,  were  it  not  for  its  philosophical  implications. 
For  Mr.  Mivart  regards  the  difference  between  conscious- 
ness and  consentience  as  a  difference  in  kind,  whereas  I 
regard  it  as  a  generic  difference.  I  believe  that  consentience 
(perceptual  consciousness)  can  piss  and  has  passed  into 
consciousness  (conceptual  consciousness)  ;  but  Mr.  Mivart 
believes  that  between  the  two  there  is  a  great  gulf  fixed, 
which  no  evolutionary  process  could  possibly  bridge  or 
span. 

The  perceptual  volition  of  animals,  then,  is  a  state  of 
consciousness  arising  when,  as  the  outcome  of  perception  and 
emotion,  motor-stimuli  prompting  to  activity  conflict  with 
inhibitory  stimuli  restraining  from  activity.  The  animal 
chooses  or  yields  to  the  stronger  motive,  and  is  conscious 
of  choosing.  But  it  cannot  reflect  upon  its  choice,  and 
bother  its  head  about  free-will.  This  involves  conceptual 
thought.  When  physiologists  have  solved  the  problem  of 
inhibition,  they  will  be  in  a  position  to  consider  that  of 
volition.  At  present  we  cannot  be  said  to  know  much 
about  it  from  the  physiological  standpoint. 

Still,  as  before  indicated,  the  fact  of  inhibition  is  un- 
questionable and  of  the  utmost  importance.  It  has  before 
been  pointed  out  that  through  inhibition,  through  the 
suppression  or  postponement  of  action,  there  has  been 
rendered  possible  that  reverberation  among  the  nervous 
processes  in  the  brain  which  is  the  physiological  concomi- 
tant of  aesthetic  and  conceptual  thought.  We  have  just 

*  In  the  sense  in  which  I  have  used  the  word ;  not  as  he  uses  it  himself. 


462 


Animal  Life  and  Intelligence. 


seen  that,  in  association  with  inhibition,  the  faculty  of 
volition  has  been  developed.  And  we  may  now  notice  that 
the  postponement  or  suppression  of  action  is  one  of  the 
criteria  of  intelligent  as  opposed  to  instinctive  or  impulsive 
activities.  This  is,  however,  subordinate  to  the  criterion 
of  novelty  and  individuality. 

Granting,  then,  that  an  action  is  shown  to  be  intelligent 
from  the  novelty  of  the  adjustments  involved,  and  from  the 
individuality  displayed  in  dealing  with  complex  circum- 
stances (instinctive  adjustments  being  long-established  and 
lacking  in  originality),  we  may  say  that  the  level  of  intelli- 
gence is  indicated  by  the  complexity  of  the  adjustments  ; 
their  precision ;  the  rapidity  with  which  they  are  made ; 
the  amount  of  prevision  they  display ;  and  in  their  being 
such  as  to  extract  from  the  surrounding  conditions  the 
maximum  of  benefit. 

Before  closing  this  chapter,  I  will  give  a  classification  of 
involuntary  and  voluntary  activities  : — 


Initiation. 

Motive. 

Kesult. 

A.  Involuntary  (auto- 

Sense-stimulus 

Unconscious  re- 

Automatic or 

matic  and  reflex) 

action  of  nerve- 

reflex  act 

centres 

B.  Involuntary  (habi- 
tual and  instinctive) 

Percept      (per- 
haps lapsed) 

Impulse      (per- 
haps lapsed) 

Involuntary  ac- 
tivity 

C.  Voluntary  (percep- 

Percept 

Appetence 

Voluntary   ac- 

tual) 

tivity 

D.  Voluntary      (con- 

Concept 

Desire 

Conduct 

ceptual) 

In  the  involuntary  acts  classed  as  automatic  and  reflex, 
the  initiation  and  the  result  may  be  accompanied  by  con- 
sciousness, but  the  intermediate  mental  link  which  answers 
to  the  motive  in  higher  activities  is,  I  think,  unconscious. 
In  habitual  and  instinctive  activities  the  consciousness  of 
the  percept  and  the  impulse  may  in  some  cases  have 
become  evanescent,  or,  to  use  G.  H.  Lewes's  phrase,  have 
lapsed.  In  the  case  of  some  instincts,  originating  by  the 
natural  selection  of  unintelligent  activities,  the  perceptual 


Habit  and  Instinct.  463 

element  may  never  have  emerged,  and  the  initiation  may 
have  been  a  mere  sense-stimulus. 

The  division  of  voluntary  activities  into  perceptual  and 
conceptual  follows  on  the  principles  adopted  and  developed 
in  this  work.  As  to  the  terminology  employed,  I  agree  with 
Mr.  S.  Alexander  *  that  it  is  convenient  to  reserve  the  terms 
"  desire  "  and  "  conduct  "  for  use  in  the  higher  conceptual 
plane.  Animals,  I  believe,  are  incapable  of  this  higher 
desire  and  this  higher  conduct.  It  only  remains  to  note 
that  it  is  within  the  limits  of  the  fourth  class  (of  voluntary 
activities  initiated  by  concepts)  that  morality  takes  its 
origin.  Morality  is  a  matter  of  ideals.  Moral  progress 
takes  its  origin  in  a  state  of  dissatisfaction  with  one's 
present  moral  condition,  and  of  desire  to  reach  a  higher 
standard.  The  man  quite  satisfied  with  himself  has  not 
within  him  this  mainspring  of  progress.  The  chief  deter- 
minant of  the  moral  character  of  any  individual  is  the 
ideal  self  he  keeps  steadily  in  view  as  the  object  of  moral 
desire — the  standard  to  be  striven  for,  but  never  actually 
attained. 

*  "  Moral  Order  and  Progress." 


464  Animal  Life  and  Intelligence, 


CHAPTER  XII. 

MENTAL    EVOLUTION. 

THE  phrase  "  mental  evolution  "  clearly  implies  the  existence 
of  somewhat  concerning  which  evolution  can  be  predicated ; 
and  the  adjective  "  mental "  further  implies  that  this  some- 
what is  that  which  we  term  "  mind."  What  is  this  mind 
which  is  said  to  be  evolved  ?  And  out  of  what  has  it  been 
evolved  ?  Can  we  say  that  matter,  when  it  reaches  the 
complexity  of  the  grey  cortex  of  the  brain,  becomes  at  last 
self-conscious  ?  May  we  say  that  mind  is  evolved  from 
matter,  and  that  when  the  dance  of  molecules  reaches  a 
certain  intensity  and  intricacy  consciousness  is  developed  ? 
I  conceive  not. 

"  If  a  material  element,"  says  Mr.  A.  R.  Wallace,*  "  or 
a  combination  of  a  thousand  material  elements  in  a  molecule, 
are  alike  unconscious,  it  is  impossible  for  us  to  believe  that 
the  mere  addition  of  one,  two,  or  a  thousand  other  material 
elements  to  form  a  more  complex  molecule  could  in  any 
way  tend  to  produce  a  self-conscious  existence.  The  things 
are  radically  distinct.  To  say  that  mind  is  a  product  or 
function  of  protoplasm,  or  of  its  molecular  changes,  is  to 
use  words  to  which  we  can  attach  no  clear  conception. 
You  cannot  have  in  the  whole  what  does  not  exist  in  any 
of  the  parts ;  and  those  who  argue  thus  should  put  forth 
a  definite  conception  of  matter,  with  clearly  enunciated 
properties,  and  show  that  the  necessary  result  of  a  certain 
complex  arrangement  of  the  elements  or  atoms  of  that 
matter  will  be  the  production  of  self-consciousness.  There 
is  no  escape  from  this  dilemma — either  all  matter  is  con- 

*  "  Contributions  to  the  Theory  of  Natural  Selection,"  p.  365. 


Mental  Evolution.  465 

scious,  or  consciousness  is  something  distinct  from  matter  ; 
and  in  the  latter  case,  its  presence  in  material  forms  is  a 
proof  of  the  existence  of  conscious  beings,  outside  of  and 
independent  of  what  we  term  '  matter.'  " 

There  is  a  central  core  of  truth  in  Mr.  Wallace's 
argument  which  I  hold  to  be  beyond  question,  though  I 
completely  dissent  from  the  conclusion  which  he  draws 
from  it.  I  do  not  believe  that  the  existence  of  conscious 
beings,  outside  of  and  independent  of  what  we  term 
"  matter,"  is  a  tenable  scientific  hypothesis.  In  which 
case,  Mr.  Wallace  will  reply,  "You  are  driven  on  to  the 
other  horn  of  the  dilemma,  and  must  hold  the  preposterous 
view  that  all  matter  is  conscious." 

Now,  I  venture  to  think  that  the  use  here  of  the  word 
"  conscious  "  is  prejudicial  to  the  fair  consideration  of  the 
view  which  I  hold  in  common  with  many  others  of  far 
greater  insight  than  I  can  lay  claim  to.  And  it  seems  to 
me  that  we  cannot  fairly  discuss  this  question  without  the 
introduction  of  terms  which,  from  their  novelty,  are  devoid 
of  the  inevitable  implications  associated  with  "mind"  and 
"  consciousness  "  and  their  correlative  adjectives.  Such 
terms,  therefore,  I  venture  to  suggest,  not  with  a  view  to 
their  general  acceptance,  but  to  enable  me  to  set  forth, 
without  arousing  at  the  outset  antagonistic  prejudice,  that 
hypothesis  which  alone,  as  it  seems  to  me,  meets  the  con- 
ditions of  the  case. 

According  to  the  hypothesis  that  is  known  as  the 
monistic  hypothesis,  the  so-called  connection  between  the 
molecular  changes  in  the  brain  and  the  concomitant  states 
of  consciousness  is  assumed  to  be  identity.  Professor 
Huxley  suggested  the  term  "  neuroses  "  for  the  molecular 
changes  in  the  brain,  and  "psychoses  "  for  the  concomitant 
states  of  consciousness.  According  to  materialism,  psychosis 
is  a  product  of  neurosis ;  but  according  to  monism,  neither 
is  psychosis  a  product  of  neurosis,  nor  is  neurosis  a  product 
of  psychosis,  but  neurosis  is  psychosis.  They  are  identical. 
What  an  external  observer  might  perceive  as  a  neurosis  of 
my  brain,  I  should  at  the  same  moment  be  feeling  as  a 


466  Animal  Life  and  Intelligence. 

psychosis.  The  neurosis  is  the  outer  or  objective  aspect ; 
the  psychosis  is  the  inner  or  subjective  aspect. 

It  is  almost  impossible  to  illustrate  this  assumption  by 
any  physical  analogies.  Perhaps  the  best  is  that  of  a 
curved  surface.  The  convex  side  is  quite  different  from 
the  concave  side.  But  we  cannot  say  that  the  concavity  is 
produced  by  the  convexity,  or  that  the  convexity  is  caused 
by  the  concavity.  The  convex  and  the  concave  are  simply 
different  aspects  of  the  same  curved  surface.  So,  too,  are 
molecular  brain-changes  (neuroses)  and  the  concomitant 
states  of  consciousness  (psychoses)  simply  different  aspects 
of  the  same  waves  on  the  troubled  sea  of  being.  Again, 
we  may  liken  the  brain-changes  to  spoken  or  written  words, 
and  the  states  of  consciousness  to  the  meaning  which 
underlies  them.  The  spoken  word  is,  from  the  physical 
point  of  view,  a  mere  shudder  of  sound  in  the  air ;  but  it 
is  also,  from  the  conceptual  point  of  view,  a  fragment  of 
analytic  thought. 

Now,  we  believe  that  the  particular  kind  of  molecular 
motion  which  we  call  neurosis,  or  brain-action,  has  been 
evolved.  Evolved  from  what?  From  other  and  simpler 
modes  of  molecular  motion.  Complex  neuroses  have  been 
evolved  from  less  complex  neuroses ;  these  from  simple 
neuroses  ;  these,  again,  from  organic  modes  of  motion  which 
can  no  longer  be  called  neuroses  at  all ;  and  these,  once 
more,  from  modes  of  motion  which  can  no  longer  be  called 
organic.  And  from  what  have  psychoses,  or  states  of  con- 
sciousness, been  evolved?  Complex  psychoses  have  been 
evolved  from  less  complex  psychoses ;  these  from  simple 
psychoses ;  these,  again,  from — what  ?  We  are  stopped  for 
want  of  words  to  express  our  meaning.  We  believe  that 
psychoses  have  been  evolved.  Evolved  from  what  ?  From 
other  and  simpler  modes  of — something  which  answers  on 
the  subjective  side  to  motion.  We  can  hardly  sa'y  "of 
consciousness ;  "  for  consciousness  answers  to  a  particular 
mode  of  motion  called  neurosis.  So  that  unless  we  are 
prepared  to  say  that  all  modes  of  motion  are  neuroses,  we 
can  hardly  say  that  all  modes  of  that  which  answers  on 


Mental  Evolution.  467 

the  subjective  side  to  motion  are  conscious.  I  shall  venture, 
therefore,  to  coin  a  word  *  to  meet  my  present  need. 

It  is  generally  admitted  that  physical  phenomena,  in- 
cluding those  which  we  call  physiological,  can  be  explained 
(or  are  explicable)  in  terms  of  energy.  It  is  also  generally 
admitted  that  consciousness  is  something  distinct  from, 
nay,  belonging  to  a  wholly  different  phenomenal  order  from, 
energy.  And  it  is  further  generally  admitted  that  con- 
sciousness is  nevertheless  in  some  way  closely,  if  not 
indissolubly,  associated  with  special  manifestations  of 
energy  in  the  nerve-centres  of  the  brain.  Now,  we  call 
manifestations  of  energy  "kinetic"  manifestations,  and  we 
use  the  term  "  kinesis  "  for  physical  manifestations  of  this 
order.  Similarly,  we  may  call  concomitant  manifestations 
of  the  mental  or  conscious  order  "  metakinetic,"  and  may 
use  the  term  "  metakinesis  "  for  all  manifestations  belong- 
ing to  this  phenomenal  order.  According  to  the  monistic 
hypothesis,  every  mode  of  kinesis  has  its  concomitant  mode  of 
metakinesis,  and  when  the  kinetic  manifestations  assume  the 
form  of  the  molecular  processes  in  the  human  brain,  the  meta- 
kinetic manifestations  assume  the  form  of  human  consciousness. 
I  am,  therefore,  not  prepared  to  accept  the  horn  of  Mr. 
Wallace's  dilemma  in  the  form  in  which  he  states  it.  All 
matter  is  not  conscious,  because  consciousness  is  the  meta- 
kinetic concomitant  of  a  highly  specialized^order  of  kinesis. 
But  every  kinesis  has  an  associated  metakinesis ;  and 
parallel  to  the  evolution  of  organic  and  neural  kinesis  there 
has  been  an  evolution  of  metakinetic  manifestations  culminating 
in  conscious  thought. 

Paraphrasing  the  words  of  Professor  Max  Muller,t  I 
say,  "  Like  Descartes,  like  Spinoza,  like  Leibnitz,  like 
Noire,  I  require  two  orders  of  phenomena  only,  but  I  define 
them  differently,  namely,  as  kinesis  and  metakinesis. 

*  I  consider  that  an  apology  is  needed  for  the  coinage  of  this  and  of  two 
or  three  other  words,  such  as  "  construct,"  "  isolate,"  arid  "  predominant."  I 
can  only  say  that  in  each  case  1  endeavoured  to  avoid  them,  but  found  that  I 
could  not  make  my  meaning  clear,  or  bring  out  the  point  I  wished  to  emphasize 
without  them. 

t  "  Science  of  Thought,"  pp.  286,  287. 


468  Animal  Life  and  Intelligence. 

According  to  these  two  attributes  of  the  noumenal, 
philosophy  has  to  do  with  two  streams  of  evolution — the 
subjective  and  the  objective.  Neither  of  them  can  be  said 
to  be  prior.  .  .  .  The  two  streams  of  evolution  run  parallel, 
or,  more  correctly,  the  two  are  one  stream,  looked  at  from 
two  opposite  shores."  And  again,*  "  Like  Noire,  I  would 
go  hand-in-hand  with  Spinoza,  and  carry  away  with  me 
this  permanent  truth,  that  metakinesis  can  never  be  the 
product  of  kinesis  (materialism),  nor  kinesis  the  product  of 
metakinesis  (spiritualism) ,  but  that  the  two  are  inseparable, 
like  two  sides  of  one  and  the  same  substance." 

According  to  this  view,  the  two  distinct  phenomenal 
orders,  the  kinetic  and  the  metakinetic,  are  distinct  only 
as  being  different  phenomenal  manifestations  of  the  same 
noumenal  series.  Matter,  the  unknown  substance  f  of 
kinetic  manifestations,  disappears  as  unnecessary ;  spirit, 
the  unknown  substance  of  metakinetic  manifestations,  also 
disappears ;  both  are  merged  in  the  unknown  substance  of 
being — unknown,  that  is  to  say,  in  itself  and  apart  from 
its  objective  and  subjective  manifestations. 

It  will,  no  doubt,  be  objected  that  the  final  identity  of 
•  neuroses  and  psychoses  is  an  assumption.  It  is  pure 
assumption,  it  will  be  said,  that  these  molecular  nervous 
processes,  and  those  percepts  and  emotions  which  are  their 
concomitants,  are  simply  different  aspects,  outer  and  inner, 
objective  and  subjective,  physiological  and  psychological,  of 
the  same  noumenal  series.  This  must  fully  and  freely  be 
admitted.  Any  and  every  explanation  of  the  connection  of 
mind  and  body  is  based  on  an  assumption.  The  common- 
place view  of  two  distinct  entities,  a  mind  which  can  act  on 
the  body  and  a  body  which  influences  the  mind,  is  a  pure 
assumption.  The  philosophic  view,  that  there  are  two 
entities,  body  and  mind,  that  neither  can  act  on  the  other, 
but  that  there  is  a  pre-established  harmony  between  the 
activities  of  the  one  and  the  activities  of  the  other,  is,  again, 
a  pure  assumption.  The  materialistic  view,  that  matter 

*  "  Science  of  Thought,"  p.  279. 

t  I  use  "  substance  "  here  in  its  philosophical  sense. 


Mental  Evolution.  469 

becomes  at  last  self-conscious,  is  a  pure  assumption.  The 
idealistic  view,  that  the  world  of  phenomena  has  no 
existence  save  as  a  fiction  of  my  own  mind,  is,  once  more, 
a  pure  assumption.  It  is  not  a  question  of  making  or  of 
not  making  an  initial  assumption ;  that  we  must  do  in  any 
case.  The  question  is — Which  assumption  yields  the  most 
consistent  and  harmonious  results  ? 

Again,  an  answer  will,  no  doubt,  be  demanded  by  some 
people  to  the  question — How  does  that  which,  objectively 
considered,  is  neurosis  become  subjectively  felt  as  psychosis  ? 
Is  not  the  identification  of  neurosis  and  psychosis  a  begging 
of  the  question,  unless  the  how,  the  modus  operandi,  is  ex- 
plained ?  If,  in  the  latter  query,  by  "  begging  the  question" 
the  adoption  of  an  initial  assumption  is  meant,  I  have 
already  answered  it  in  the  affirmative.  To  the  direct 
question — How  does  the  objective  neurosis  become  conscious 
as  a  subjective  psychosis  ? — while  freely  admitting  that  I  do 
not  know,  I  enter  the  protest  that  it  is  philosophically  an 
illegitimate  question ;  for  an  answer  is  impossible  without 
transcending  consciousness.  An  illustration  will,  perhaps, 
make  my  meaning  clear.  Suppose  that  a  sentient  being 
be  enclosed  within  a  sphere  of  opaque  but  translucent 
ground  glass,  into  the  substance  of  which  there  are  wrought 
certain  characters.  Suppose  that  external  to  this  there  is 
another  similar  but  larger  sphere,  similarly  inscribed,  and 
that  a  second  sentient  being  is  enclosed  in  the  space  between 
the  two  spheres.  By  an  attentive  study  of  the  two  spheres, 
this  second  sentient  being  arrives  at  the  conclusion  that 
the  markings  on  the  convex  surface  of  the  inner  sphere 
answer  to  the  markings  on  the  concave  surface  of  the  outer 
sphere ;  and  he  is  led  to  the  conviction  that  what  he  sees 
as  markings  on  the  convex,  the  being  within  the  sphere 
sees  as  markings  on  the  concave.  He  is,  however,  perplexed 
by  the  question — How  can  this  be  ?  He  is  acquainted  with 
a  certain  inner  surface  and  a  certain  outer  surface.  He  is 
led  to  correlate  the  markings  of  the  one  with  the  markings 
of  the  other.  But  the  question  how  the  two  can  have  such 
different  aspects  is  beyond  his  solution.  Puzzle  as  he 


470  Animal  Life  and  Intelligence. 

may,  he  can  never  solve  it.  It  can  only  be  solved  (and 
how  simple  then  the  solution!)  by  a  being  outside  both 
spheres,  who  can  see  what  the  enclosed  being,  "  cabin'd, 
cribb'd,  confined,"  could  never  see,  namely,  that  the 
characters  were  wrought  in  the  translucent  glass  of  the 
spheres.  By  which  parable,  imperfect  as  it  is,  I  would 
teach  that  we  can  never  learn  how  kinetic  manifestations 
have  a  metakinetic  aspect  without  getting  outside  ourselves 
to  view  kinesis  and  metakinesis  from  an  independent 
standpoint.  Or,  in  the  words  of  Sir  W.  E.  Hamilton,* 
''How  consciousness  in  general  is  possible;  and  how,  in 
particular,  the  consciousness  of  self  and  the  consciousness 
of  something  different  from  self  are  possible  .  .  .  these 
questions  are  equally  unphilosophical,  as  they  suppose  the 
possibility  of  a  faculty  exterior  to  consciousness  and  con- 
versant about  its  operations." 

The  only  course  open  to  us,  then,  in  this  difficult  but 
important  problem  is  to  make  certain  assumptions,  and 
see  how  far  a  consistent  hypothesis  may  be  based  upon 
them.  I  make,  therefore,  the  following  assumptions : 
First,  that  there  is  a  noumenal  system  of  "things  in  them- 
selves "  of  which  all  phenomena,  whether  kinetic  or  meta- 
kinetic, are  manifestations.  Secondly,  that  whenever  in 
the  curve  of  noumenal  sequences  kinetic  manifestations 
(convexities)  appear,  there  appear  also  concomitant  meta- 
kinetic manifestations  (concavities).  Thirdly,  that  when 
kinetic  manifestations  assume  the  integrated  and  co- 
ordinated complexity  of  the  nerve-processes  in  certain 
ganglia  of  the  human  brain,  the  metakinetic  manifestations 
assume  the  integrated  and  co-ordinated  complexity  of  human 
consciousness.  Fourthly,  that  what  is  called  "mental 
evolution"  is  the  metakinetic  aspect  of  what  is  called 
brain  or  interneural  evolution. 

It  would  require  far  more  space  than  I  can  here  com- 
mand to  deal  adequately  with  these  assumptions,  and  meet 
the  objections  which  have  been  and  are  likely  to  be  raised 
against  them.  I  must  content  myself  with  drawing  atten- 
*  Quoted  in  Professor  Veitch's  "  Hamilton,"  p.  77. 


Mental  Evolution.  471 

tion  to  one  or  two  which  seem  at  once  obvious  and  yet 
easily  met. 

It  may  be  asked — What  advantage  has  such  a  view  over 
realistic  materialism  ?  Why  not  assume  that  neural  pro- 
cesses, when  they  reach  a  certain  complexity,  give  rise  to 
or  produce  consciousness  ? 

First  of  all,  I  think,  the  objection  raised  by  Mr.  Wallace, 
in  the  passage  before  quoted,  to  materialism  is  unanswer- 
able. Secondly,  realistic  materialism  ignores  the  fact  that 
kinetic  manifestations  for  us  human-folk  are  phenomena  of 
consciousness.  To  this  we  will  return  presently.  Thirdly, 
realistic  materialism,  and  any  view  which  regards  the 
physical  series  as  one  which  is  independent  of  the  psychical 
accompaniments,  and  which  regards  consciousness  as  in 
any  sense  a  by-product  of  neural  processes,  are  open  to  an 
objection  which  was  forcibly  stated  by  the  late  Professor 
Herbert.*  "  It  is  clearly  impossible,"  he  says,  "  for  those 
.  .  .  who  teach  that  consciousness  is  [a  by-product  and] 
never  the  cause  of  physical  change,  to  dispute  that  the 
actions,  words  and  gestures  of  every  individual  of  the 
human  race  would  have  been  exactly  what  they  have  been 
in  the  absence  of  mind  ;  had  mind  been  wanting  [had  the 
by-product  never  emerged],  the  same  empires  would  have 
risen  and  fallen,  the  same  battles  would  have  been  fought 
and  won,  the  same  literature,  the  same  masterpieces  of 
painting  and  music  would  have  been  produced,  the  same 
religious  rites  would  have  been  performed,  and  the  same 
indications  of  friendship  and  affection  given.  To  this 
absurdity  physical  science  [realistic  materialism]  stands 
committed."  I  believe  that  Professor  Herbert's  argument, 
of  which  this  passage  is  a  summary,  is,  as  against  realistic 
materialism,  sound  and  unanswerable.  Finally,  as  Pro- 
fessor Max  Miiller  has  well  observed,!  "  Materialism  may 
in  one  sense  be  said  to  be  a  grammatical  blunder ;  it  is  a 
misapplication  of  a  word  which  can  be  used  in  an  oblique 

*  T.  M.   Herbert,    "The    Kealistic    Assumptions    of   Modern    Science 
Examined,"  2nd  edit.,  p.  123. 

t  "  Science  of  Thought,"  p.  571. 


472  Animal  Life  and  Intelligence. 

sense  only,  but  which  materialists  use  in  the  nominative. 
In  another  sense  it  is  a  logical  blunder,  because  it  rests 
on  a  confusion  between  the  objective  and  the  subjective. 
Matter  can  never  be  a  subject,  it  can  never  know,  be- 
cause the  name  was  framed  to  signify  what  is  the  object 
of  our  knowledge  or  what  can  be  known."  Materialism, 
then,  for  more  than  one  sufficient  reason,  stands  con- 
demned. 

It  should  be  stated,  however,  that  Professor  Herbert 
seems  to  regard  the  monistic  view  I  am  advocating  as 
committed  to  the  absurdity  indicated  in  the  passage  I  have 
quoted.  I  am  convinced  that  he  was  here  in  error.  Indeed, 
he  seems  to  have  failed  to  see  the  full  bearing  of  the 
monistic  hypothesis ;  for  while  he  combats  it,  he  comes 
very  near  adopting  it  himself.  With  this,  however,  I  have 
no  concern.  I  have  only  to  show  that,  on  the  assumptions 
above  set  down,  we  are  not  committed  to  the  "  absurdity  " 
of  supposing  that  intelligence  and  consciousness  have  had 
no  influence  on  the  course  of  events  in  organic  evolution — 
that  they  have  only  felt  the  inevitable  sequence  of  physical 
phenomena  without  in  any  way  influencing  it.  According 
to  the  monistic  hypothesis,  kinesis  and  metakinesis  are  co- 
ordinate. The  physiologist  may  explain  all  the  activities 
of  men  and  animals  in  terms  of  kinesis.  The  psychologist 
may  explain  all  the  thoughts  and  emotions  of  man  in  terms 
of  metakinesis.  They  are  studying  the  different  phenomenal 
aspects  of  the  same  noumenal  sequences.  It  is  just  as 
absurd  to  say  that  kinetic  manifestations  would  have  been 
the  same  in  the  absence  of  metakinesis,  as  to  say  that  the 
metakinetie  manifestations,  the  thoughts  and  emotions, 
would  have  been  the  same  in  the  absence  of  kinesis.  It  is 
just  as  absurd  to  say  that  the  physical  series  would  have 
been  the  same  in  the  absence  of  mind,  as  to  say  that  the 
mental  series  would  have  been  the  same  in  the  absence  of 
bodily  organization.  For  on  this  view  consciousness  is  no 
mere  by-product  of  neural  processes,  but  is  simply  one 
aspect  of  them.  You  cannot  abstract  (except  in  thought 
and  by  analysis)  metakinesis  from  kinesis ;  for  when  you 


Mental  Evolution.  473 

have  taken  away  the  one,  you  have  taken  the  other  also. 
To  speak  of  the  organic  activities  being  conceivably  the 
same  in  the  absence  of  consciousness,  is  like  saying  that 
the  outer  curve  of  a  soap-bubble  would  be  the  same  in  the 
absence  of  the  inner  curve.  Whatever  hypothetical  exist- 
ences this  statement  may  be  true  of,  it  assuredly  is  not 
true  of  soap-bubbles. 

To  pass  on  from  this  point  to  another,  it  is  possible — I 
trust  not  probable,  but  still  not  impossible — that  some 
one  may  say,  "But  how,  on  this  view,  can  perception  be 
accounted  for  ?  Granted  that  in  the  neural  processes  of 
the  individual  organism  kinesis  is  accompanied  by  those 
metakinetic  manifestations  which  we  term  '  consciousness,' 
how  will  this  account  for  our  perception  of  a  distant  object  ? 
Yonder  scarlet  geranium  is  a  centre  of  kinetic  manifesta- 
tions ;  it  is  fifty  yards  and  more  away.  How  can  I  here, 
by  any  metakinetic  process,  perceive  the  kinesis  that  is  going 
on  out  there  ?  " 

For  one  who  can  ask  this  question,  I  have  written  the 
chapter  on  "  Mental  Processes  in  Man,"  and  have  used  the 
term  "  construct,"  in  vain.  In  vain  have  I  endeavoured  to 
explain  that  the  seat  of  all  mental  processes  is  somewhere 
within  the  brain ;  in  vain  have  I  indicated  the  nature  of 
localization  and  outward  projection ;  in  vain  have  I  reiterated 
that  the  object  is  a  thing  we  construct  through  a  (meta- 
kinetic) activity  of  the  mind  ;  in  vain  have  I  insisted  that 
our  knowledge  is  merely  symbolic  of  the  noumenal  existence ; 
and  perhaps  in  vain  shall  I  again  endeavour  to  make  my 
meaning  clear. 

When  we  say  that  we  perceive  an  object,  the  mental 
process  (perception)  is  the  metakinetic  equivalent  of  certain 
kinetic  changes  among  the  brain-molecules.  The  object, 
as  an  object  (as  a  phenomenon  or  appearance),  is  there 
generated.  As  before  stated,  I  assume  the  existence  of  a 
noumenal  system  of  which  the  noumenal  existence,  sym- 
bolized as  object,  is  a  part.  But  what  we  term  the  object 
is  a  certain  phase  of  metakinesis  accompanying  certain 
kinetic  nerve-processes  in  the  brain.  In  other  words, 


474  Animal  Life  and  Intelligence. 

phenomena  are  states  of  consciousness,  and  cannot,  for 
the  percipient,  be  anything  else. 

"  It  comes  to  this,  then,"  an  idealist  will  interpose : 
"  states  of  consciousness  are  metakinetic ;  phenomena  are 
states  of  consciousness ;  therefore  phenomena  are  meta- 
kinetic. Your  kinesis  vanishes,  and  you  are  one  with  us, 
a  pure  idealist." 

Before  showing  wherein  I  am  not  a  pure  idealist,  let  me 
state  why  I  am  not.  For  the  pure  idealist,  phenomena 
being  states  of  consciousness,  and  nothing  more,  the  world 
around  resolves  itself  into  an  individual  dream.  Were  I  to 
hold  this  view,  this  pen  which  I  hold,  this  table  at  which  I 
write,  the  spreading  trees  outside  my  window,  my  little  sons 
whose  merry  voices  I  can  hear  in  the  garden,  my  very  body 
and  limbs,  all  are  merely  states  of  my  own  consciousness. 
This  I  am  not  prepared  to  accept.  Do  what  I  will,  I  cannot 
believe  that  such  an  interpretation  of  the  facts  is  true. 

For  this  reason  I  make  my  first  assumption  that  there 
is  a  noumenal  system  of  things  in  themselves,  of  which  all 
phenomena,  whether  kinetic  or  metakinetic,  are  manifesta- 
tions. I  differ  from  the  pure  idealist  in  that  I  believe  that 
phenomena,  besides  being  states  of  consciousness,  have 
another,  namely,  a  kinetic,  aspect.  What  are  for  me  states 
of  consciousness  are  for  you  neural  processes  in  my  brain. 
These  are,  again,  for  you  states  of  consciousness ;  but  still 
for  some  one  else  they  are  kinetic  processes.  And  an 
ordinary  extraneous  object,  like  this  table,  is  the  phenomenal 
aspect  to  me  of  a  noumenal  existence ;  and  since  that 
noumenal  existence  appears  to  you  also  in  like  phenomenal 
guise,  the  table  is  an  object  for  you  as  well  as  for  me,  and 
not  only  for  us,  but  for  all  sentient  beings  similarly  con- 
stituted. The  world  we  live  in  is  a  world  of  phenomena  ; 
and  it  has  a  phenomenal  reality  every  whit  as  valid  as  the 
noumenal  reality  which  underlies  it.  And  that  phenomenal 
reality  has  two  aspects — an  inner  aspect  as  metakinesis, 
and  an  outer  aspect  as  kinesis. 

I  must  not  here  further  develop  the  manner  in  which 
the  hypothesis  of  monism  presents  itself  to  my  mind.  I 


Mental  Evolution.  475 

will  only,  before  passing  on  to  consider  mental  or  meta- 
kinetic  evolution,  draw  passing  attention  to  two  matters. 
We  have  seen  that  Professor  Hering  and  Mr.  Samuel 
Butler  have  suggested  "organic  memory  "  as  a  conception 
useful  for  the  comprehencion  of  embryonic  reconstruction 
in  development  and  other  such  matters  (see  p.  62).  On  the 
hypothesis  of  monism,  this  may  be  regarded  as  a  kinetic 
manifestation  of  that  which  in  memory  rises  to  the  meta- 
kinetic  level  of  consciousness. 

The  other  matter  is  of  far  wider  import.  Monism 
affords  a  consistent  and  comprehensible  theory  of  the  ego, 
or  conscious  self — that  which  endures  amid  the  flux  and 
reflux  of  our  conscious  states.  The  ego,  or  self,  is  that 
matakinetic  unity  which  answers  to,  or  is  the  inner  aspect 
of,  the  kinetic  unity  of  the  organism.*  Only  here  and 
there,  in  fleeting  and  changing  series,  does  the  metakinesis 
rise  to  the  level  of  consciousness.  But  the  metakinetic 
unity  is  as  completely  one,  indivisible,  and  enduring,  as  is 
the  physical  organism  which  is  its  kinetic  counterpart. 
No  one  questions  that  there  is  an  enduring  organism  of 
which  certain  visible  activities  are  occasional  manifesta- 
tions ;  no  one  who  has  adequately  grasped  the  teachings  of 
monism  can  question  that  the  enduring  ego,  of  which 
certain  states  of  consciousness  are  occasional  manifestations, 
is  the  metakinetic  equivalent  of  the  organic  kinesis.  This 
solution  of  a  problem  which  baffles  alike  materialists  and 
idealists  is,  as  it  seems  to  me,  as  satisfactory  as  it  is 
simple. 

And  now  let  us  pass  on  to  consider  the  question  of 
mental  or  metakinetic  evolution.  What,  on  the  principles 
above  laid  down,  can  we  be  said  to  know  or  have  learnt 
about  it  ? 

The  inevitable  isolation  of  the  individual  mind  has  long 
been  recognized.  "  Such  is  the  nature  of  spirit,  or  that 
which  acts,"  says  Bishop  Berkeley,  "  that  it  cannot  be 

*  Strictly  speaking,  of  the  brain;  but  since  the  brain  has  no  organic 
independence  of  the  body,  it  is  best  here  to  focus  attention  on  the  unity  of  the 
organism. 


476  Animal  Life  and  Intelligence. 

itself  perceived,  but  only  by  the  effects  that  it  produceth." 
"  Thinking  things,  as  such,"  writes  Kant,  "  can  never  occur 
in  the  outward  phenomena ;  we  can  have  no  outward  per- 
ception of  their  thoughts,  consciousness,  desires ;  for  all 
this  is  the  domain  of  the  inward  sense."  How  comes  it, 
then,  that  there  is  nothing  of  which,  practically  speaking, 
we  are  more  firmly  convinced  than  that  our  neighbours 
have  each  a  consciousness  more  or  less  similar  to  our 
own  ?  Certain  it  is  that  no  one  can  come  into  sensible 
contact  with  his  brother's  personality  and  essential  spirit. 
My  brother's  soul  can  never  stand  to  me  in  the  relation  of 
object.  Subject  he  never  can  be  to  any  but  himself.  What, 
then,  is  he — his  metakinetic  self,  not  his  kinetic  material 
body — to  me  ?  In  Clifford's  convenient  phrase,  he  is  an 
eject.  And  what  is  an  eject  ?  An  eject  is  a  more  or  less 
modified  image  of  myself,  that  I  see  mirrored,  as  in  a  glass 
darkly,  in  the  human-folk  around  me.  Into  every  human 
brother  I  breathe  the  spirit  of  this  eject,  and  he  becomes 
henceforth  to  me  a  living  soul.  Or,  if  this  mode  of 
presentation  does  not  meet  with  approval,  I  will  say  that 
an  eject  is  that  metakinetic  unity  I  infer  as  identically 
associated  with  the  organic  and  kinetic  unity  of  my 
brother's  living  body.  And  I  base  the  close  metakinetic 
correspondence  that  I  infer  on  the  close  kinetic  corre- 
spondence that  I  observe.  But  since  the  only  form  or 
kind  of  metakinesis  that  I  know  is  that  of  human  self- 
conscious  personality,  it  is  certain  that  the  metakinetic 
eject  is  an  image  of  myself;  it  is  and  must  be,  in  a  word, 
anthropomorphic . 

Too  much  stress  can  scarcely,  I  think,  be  laid  on  the 
human,  nay,  even  the  individual,  nature  of  the  eject.  All 
other-mind  I  am  bound  to  think  of  in  terms  of  my  own 
mind.  The  men  and  women  I  see  around  me  are  like 
curved  mirrors,  in  which  I  see  an  altered  reflection  of  my 
own  mental  features.  By  certain  signs  I  may  be  able  to 
infer  in  this  or  that  human  mirror  graces  or  imperfections 
that  I  lack.  But  throughout  my  survey  of  human  nature, 
every  estimate  of  intellectual  or  moral  elevation  or  degra- 


Mental  Evolution.  477 

dation  that  I  form  must  ever  be  measured  in  terms  of 
my  own  subjective  base-line.  My  conception  of  humanity 
must  always  be,  not  only  anthropomorphic,  but  idiomorphic. 

Once  more,  let  it  be  remembered  that  the  metakinesis 
that  rises  to  the  level  of  consciousness  is  that  which  forms 
the  inner  aspect  of  the  neural  kinesis  of  my  brain  or  yours. 
For  each  of  us,  then,  that  metakinesis  is  the  only  possible 
metakinesis  which  we  can  know  as  such  and  at  first-hand. 
And  for  the  pure  idealist  it  is  the  only  metakinesis  which 
he  can  know  at  all.  Not  so  with  us.  We  have  assumed  a 
noumenal  system  of  "things  in  themselves,"  of  which  all 
phenomena,  whether  kinetic  or  metakinetic,  are  manifesta- 
tions. We  have  assumed  that  kinesis  cannot  emerge  into 
the  light  of  being  without  casting  its  inseparable  metakinetic 
shadow.  We  have  assumed  that  when  the  kinetic  mani- 
festations assume  the  integrated  and  co-ordinated  complexity 
of  nerve-processes  in  certain  ganglia  of  the  human  brain, 
the  metakinetic  manifestations  assume  the  integrated  and 
co-ordinated  complexity  of  human  consciousness.  Human 
physiology  is  teaching  us  more  clearly  every  day  that  all 
human  activities  are,  physically  speaking,  the  outcome  of 
neural  processes.  Such  neural  processes  are  in  us  con- 
scious. Therefore,  granting  our  assumptions,  the  conclusion 
that  my  neighbour  is  a  conscious  self,  just  as  I  am,  is  not 
only  legitimate,  but  (as  we  see  from  the  daily  conduct  of 
men)  inevitable.  In  other  words,  certain  kinetic  phenomena 
have  for  us  inevitable  metakinetic  implications. 

Now,  when  we  pass  from  man  to  the  lower  animals, 
the  metakinetic  implications  become  progressively  less  in- 
evitable and  less  forcible  as  the  kinesis  becomes  more 
dissimilar  from  that  which  obtains  in  the  human  organism. 
The  only  metakinesis  that  we  know  directly  is  our  own 
human  consciousness.  In  terms  of  this  we  have  to  in- 
terpret all  other  forms  of  metakinesis. 

It  is  unnecessary  to  go  over  again  the  ground  that  has 
already  been  covered  in  previous  chapters,  in  which  we 
have  endeavoured  to  give  some  account  of  what  seem  to  us 
the  legitimate  inferences  concerning  the  mental  processes 


478  Animal  Life  and  Intelligence. 

in  animals.  The  point  on  which  I  wish  here  to  insist  is 
that,  outside  ourselves,  we  can  only  know  metakinesis  in 
and  through  its  correlative  kinesis.  Underlying  kinetic 
evolution,  we  see  that,  on  the  hypothesis  of  monism,  there 
must  have  been  metakinetic  evolution.  But  of  this  mental 
or  metakinetic  evolution  we  neither  have  nor  can  have 
independent  evidence.  Such  evolution  is  the  inevitable 
monistic  corollary  from  kinetic  evolution.  More  than  this 
it  is  not  and  cannot  be.  And  only  on  the  monistic 
hypothesis,  as  it  seems  to  me,  is  it  admissible  to  believe  in 
mental  evolution,*  properly  so  called. 

But  does  not,  it  may  be  asked,  the  hypothesis  of 
monism,  if  carried  to  its  logical  conclusion,  involve  the 
belief  in  a  world-consciousness  on  the  one  hand,  and  a 
crystal-consciousness  on  the  other?  If,  according  to  the 
hypothesis,  every  form  of  kinesis  has  also  its  metakinetic 
aspect,  "must  we  not  maintain,"  in  the  words  of  Mr.  J.  A. 
Symonds,  "  that  the  universe  being  in  one  rhythm,  things 
less  highly  organized  than  man  possess  consciousness  in 
the  degree  of  their  descent,  less  acute  than  man's  ?  Must 
we  not  also  surmise  that  ascending  scales  of  existence, 
more  highly  organized,  of  whom  we  are  at  present  ignorant, 
are  endowed  with  consciousness  superior  to  man's  ?  Is  it 
incredible  that  the  globe  on  which  we  live  is  vastly  more 
conscious  of  itself  than  we  are  of  ourselves  ;  and  that  the 
cells  which  compose  our  corporeal  frame  are  gifted  with  a 
separate  consciousness  of  a  simpler  kind  than  ours  ?  "  To 
such  questions  W.  K.  Clifford  replied  with  an  emphatic 
negative.  "  Unless  we  can  show,"  he  said,  as  interpreted 
by  Mr.  Romanes,!  "  in  the  disposition  of  the  heavenly 

*  I  ought  not  to  pass  over  without  notice  the  "  psychological  scale  "  which 
Mr.  Romanes  introduces  in  a  table  prefixed  to  "  Mental  Evolution  in  Animals." 
It  would  be  unjust  to  criticize  this  too  closely,  for  it  is  admittedly  provisional 
and  tentative.  If  such  a  scheme  is  to  be  framed,  I  would  suggest  that  the 
various  phyla  of  the  animal  kingdom  be  kept  distinct  I  question,  however, 
whether  any  one  can  produce  a  scheme  which  any  other  independent  observer 
will  thoroughly  endorse.  And  I  am  inclined  to  think  that  the  wisest  plan  id 
to  tabulate  the  kinetic  manifestations  which  we  can  actually  observe  rather 
than  the  metakineses  of  which  we  can  have  no  independent  knowledge. 

t  Contemporary  Bedew,  July,  1 886.  See  Clifford's  "  Lectures  and  Essays,' ' 
ToL  L  pp.  72  and  248 ;  vol.  ii.  p.  67. 


Mental  Evolution.  479 

bodies  some  morphological  resemblance  to  the  structure  of 
a  human  brain,  we  are  precluded  from  rationally  entertain- 
ing any  probability  that  self-conscious  volition  belongs  to 
the  universe." 

I  conceive  that  both  parties,  opposed  as  they  seem,  are 
logically  right ;  and  I  venture  to  think  that  the  terms  I 
have  suggested  will  help  us  here.  Mr.  Symonds  used  the 
word  "  consciousness  "  to  signify  metakinesis  in  general ; 
Clifford  used  it  to  signify  that  particular  kind  of  meta- 
kinesis which  in  the  human  brain  rises  to  the  level  of  con- 
sciousness. Not  only  is  it  not  inconceivable,  but  it  is  a 
logical  necessity  on  the  hypothesis  of  monism,  that  answer- 
ing to  the  kinetic  rhythm  of  the  universe  there  is  a  meta- 
kinetic  rhythm ;  but  unless  the  gyrations  of  the  spheres 
have  some  kinetic  resemblance  to  the  dance  of  molecules 
in  the  human  brain,  the  metakinesis  cannot  be  inferred  to 
be  similar  to  the  consciousness  of  man. 

Similarly,  with  regard  to  the  supposed  self-consciousness 
of  the  so-called  social  organism.  Mr.  Eomanes,  in  his  article 
on  "  The  World  as  an  Eject,"  *  leads  up  to  his  conception 
of  a  world-eject  through  the  conception  of  a  society-eject — 
an  eject,  he  tells  us,  that,  for  aught  that  any  one  of  its 
constituent  personalities  can  prove  to  the  contrary,  may 
possess  self-conscious  personality  of  the  most  vivid  character. 
Its  constituent  human  minds  may  be  born  into  it,  and  die 
out  of  it,  as  do  the  constituent  cells  of  the  human  body ;  it 
may  feel  the  throes  of  war  and  famine,  rejoice  in  the  com- 
forts of  peace  and  plenty ;  it  may  appreciate  the  growth  of 
civilization  in  its  passage  from  childhood  to  maturity. 

This,  of  course,  may  be  so  ;  or  it  may  not.  Who  can 
tell?  But  Clifford- was  on  firm  monistic  ground  when  he 
maintained  that,  unless  the  kinesis  be  similar,  we  have  no 
grounds  for  inferring  similarity  of  metakinesis. 

The  study  of  kinesis  leads  us  to  recognize  different 
kinds  or  modes  of  its  manifestation.  There  is  one  mode 
of  kinesis  in  the  circling  of  the  planets  around  the  sun, 
another  mode  of  kinesis  in  the  orderly  evolutions  of  a  great 

*  Contemporary  Review,  July,  1886. 


480  Animal  Life  and  Intelligence. 

army,  another  mode  in  the  throb  of  a  great  printing-press ; 
there  is  one  mode  of  kinesis  in  the  quivering  molecules  of 
the  intensely  heated  sun,  another  in  the  wire  that  flashes 
our  thought  to  America,  and  yet  another  in  the  molecular 
vibrations  of  the  human  brain.  All  are  of  the  same  order, 
all  are  kinetic.  But  they  differ  so  widely  in  mode  that 
each  requires  separate,  patient,  and  long-continued  study. 
So  is  it,  we  may  conclude,  with  metakinesis.  There  may 
be,  nay,  there  must  be,  many  modes.  But  our  knowledge 
is  confined  to  one  mode — that  in  which  the  metakinesis 
assumes  the  form  of  human  consciousness. 

I  have  been  led  to  discuss  this  matter  in  order  further 
to  indicate  the  inevitable  limits  of  our  knowledge  of  meta- 
kinetic  evolution.  Our  conclusions  may  be  thus  sum- 
marized :  First,  we  can  know  directly  only  one  product  of 
metakinetic  evolution — that  revealed  in  our  own  conscious- 
ness. Secondly,  the  process  of  metakinetic  evolution  must 
be  reached,  if  reached  at  all,  indirectly  through  a  study  of 
kinetic  evolution.  Thirdly,  we  have  no  right  to  infer  a 
mode  of  metakinesis  analogous  to  human  consciousness, 
unless  the  mode  of  kinesis  is  analogous  to  that  which  is 
observed  in  neural  processes.  And,  fourthly,  the  closer  the 
kinetic  resemblance  we  observe,  the  closer  the  metakinetic 
resemblance  we  may  infer. 

The  last  point  we  have  to  notice,  and  it  is  by  no  means 
an  unimportant  one,  is  that,  just  as  the  kinetic  evolution  of 
the  organism  must  be  studied  in  reference  to  its  kinetic 
environment,  so,  too,  must  the  metakinetic  evolution  of 
mind  be  studied  in  reference  to  4its  metakinetic  or  mental 
environment. 

Of  course,  in  ordinary  speech,  and  even  in  careful 
scientific  description,  we  are  forced,  if  we  would  avoid 
pedantry,  to  skip  backwards  and  forwards  from  the  kinetic 
to  the  metakinetic.  We  speak  of  a  kinetic  cow  giving  rise 
to  metakinetic  fear,  and  this  determining  certain  kinetic 
activities.  Why  we  thus  interpose  a  mental  link  in  a 
physical  series  has  already  been  explained.  The  physical 


Mental  Evolution.  481 

cow  we  know,  the  physical  activities  we  know,  the  physical 
neuroses  we  scarcely  know  at  all.  On  the  other  hand,  fear 
we  have  ourselves  experienced,  and  know  well.  Hence  we 
introduce  the  mental  link  that  we  know  in  place  of  the 
physical  link  of  which  we  are  ignorant.  And  there  can  be 
no  harm  in  our  doing  so  when  we  are  working  on  the 
practical,  and  not  the  philosophical  plane.  But  when  we 
are  striving  to  go  deeper,  and  are  employing  that  gift  of 
analysis  which  is  man's  prerogative,  in  order  to  proceed  to 
a  higher  and  more  complete  synthesis, — then  we  must  be 
careful  to  keep  separate  those  processes  which  analysis 
discloses  to  be  distinct.  And  I  repeat  that,  on  the  philoso- 
phical plane  of  thought,  we  must  remember  that  metakineses 
are  determined  by  other  metakineses,  and  by  them  alone. 

The  reader  who  has  kept  his  head  among  these  slippery 
places  will  at  once  see  that  this  is  and  must  be  so ;  for, 
as  we  have  already  seen  (p.  474),  all  phenomena  are  states 
of  consciousness,  whatever  else  they  may  also  be.  The  cow, 
as  a  phenomenon,  is  a  construct,  a  product  of  mental 
activity,  and  woven  out  of  states  of  consciousness.  For  the 
pure  idealist  she  is  this  and  nothing  more.  But  for  us  she 
is  a  real  external  entity,  manifested  thrpugh  phenomenal 
kineses.  Hence  in  ordinary  speech  we  separate  the  kinetic 
cow  from  its  metakinetic  symbols  in  consciousness  (the 
convex  from  the  concave  aspect),  and  call  the  former  the 
cow  itself,  and  the  latter  our  idea  of  the  cow.  But,  as 
before  maintained,  my  idea  of  an  object  is  for  me^the  object. 
And  this  is  now  justified  by  our  deeper  analysis. 

The  physiologist,  dealing  with  organic  phenomena  in 
terms  of  motion  (kinesis),  proclaims  that  the  physical  series 
is  complete,  that  there  is  no  necessity  for  the  introduction 
of  feeling  which  is  at  best  but  a  by-product.  The  idealist, 
dealing  with  the  processes  of  thought  and  emotion  in  terms 
of  consciousness,  proclaims  that  his  series  is  complete — an 
external  material  universe  is  an  unnecessary  encumbrance. 
Each  proclaims  a  half-truth ;  each  sees  that  half  of  the 
truth  which  alone  is  visible  from  his  special  standpoint. 
Monism  combines  the  two  (and  is,  of  course,  scouted  by 

2i 


482  Animal  Life  and  Intelligence. 

both).  It  sees  not  only  that  the  one  series  does  not  in  any 
case  interfere  with  the  other,  but  that  the  conception  of 
such  an  interference  involves  an  impossibility  and  incon- 
gruity. As  soon  could  one  speak  of  the  convexities  of  one 
side  of  a  curved  surface  interfering  with  the  corresponding 
concavities  of  the  other  side,  as  of  the  metakinetic  series 
interfering  with  the  kinetic  series,  which  is  its  other  aspect. 
But  if  the  one  cannot  interfere  with  the  other,  neither  can 
the  one  exist  without  the  other.  To  apply  the  same 
analogy,  as  well  might  one  speak  of  the  convexities  of  a 
curved  surface  existing  without  the  concavities  of  its  other 
side,  as  of  the  kinetic  phenomena  of  organic  life  as  being  con- 
ceivably the  same  in  the  absence  of  conscious  intelligence. 

Eemembering,  then,  that  just  as  the  environment  of 
kinetic  phenomena  is  itself  kinetic,  with  which  conscious- 
ness can  in  no  wise  interfere,  so  is  the  environment  of 
metakinetic  phenomena,  perception,  thought,  and  emotion, 
itself  metakinetic.  Let  us  now  proceed  to  consider  some  of 
the  implications. 

We  have  already  seen  that,  in  what  we  may  regard  as 
the  earlier  phases  of  organic  and  mental  life,  the  series 
between  stimulus,  and  activity  is  a  simple  one,  which  may 
be  kinetically  represented  thus — 

Stimulus  — ^  neural  processes  — >  motor-activities ; 

but  that  when  inhibition  is  developed,  there  arises  an 
alternative,  thus — 

^»  motor-activities. 
Stimulus-^  neural  processes  ^  .^.^  ^^ 

And  we  further  saw  that,  as  a  result  of  this  inhibition,  the 
entering  stimuli,  instead  of,  as  it  were,  rapidly  running  out 
of  the  organism  in  motor-activities,  set  up  a  more  and 
more  complex  series  of  diffused  and  reverberating  neural 
processes  in  the  brain  or  other  central  ganglia. 

From  the  metakinetic  view-point  these  diffused  and 
reverberating  neural  processes  in  the  brain  culminate  in 
consciousness  as  thought,  aesthetic  emotion,  and  the  higher 
conceptual  mental  activities.  Deeply  as  these  influence 


Mental  Evolution.  483 

conduct,  they  are,  to  a  large  extent,  independent  of  con- 
duct. A  man's  thoughts  and  aesthetic  yearnings  may  be  of 
the  truest  and  purest;  but  in  the  moment  of  temptation 
and  action,  when  stimuli  crowding  in  run  through  rapidly 
to  action,  he  falls  away.  His  conduct  belies  his  ideals. 
Nevertheless,  the  ideals  were  there,  but  too  far  away  in  the 
region  of  thought  and  abstract  aesthetics  to  be  operative  in 
action. 

Now,  we  may  divide  the  metakinetic  concomitants  of 
neural  processes  into  two  categories :  first,  those  which  are 
intimately  associated  with  neural  processes  directly  leading 
to  motor-activities ;  secondly,  those  which  are,  so  to  speak, 
floated  off  from  these  into  the  region  of  thought  and 
aesthetic  emotion,  and  which  are  therefore  associated  with 
neural  processes  only  indirectly  or  remotely  leading  to 
motor-activities.  Both  have,  of  course,  kinetic  equivalents 
in  neural  processes,  but  the  former  are  directly  associated 
with  activities  and  conduct,  and  the  latter  are  not. 

Let  me  exemplify.  Interpretations  of  nature,  theories, 
hypotheses,  belong  to  the  latter  class.  Their  association 
with  activities  is  in  the  main  indirect.  Whether  we  believe 
in  materialism,  idealism,  or  monism,  our  conduct  is  much 
the  same.  People  got  out  of  the  way  of  falling  stones, 
and  guarded  against  being  caught  by  the  incoming  tide, 
before  science  comprised  both  phenomena  under  the  theory 
of  gravitation.  The  conduct  of  human-folk  was  not  much 
altered  by  the  replacement  of  the  geocentric  by  a  helio- 
centric explanation  of  the  solar  system.  It  matters  not 
much  how  a  man  explains  the  lightning's  flash  so  long  as 
he  avoids  being  struck.  The  bird  continues  to  soar  quite 
irrespective  of  man's  prolonged  discussion  of  how  it  can  be 
explained  on  mechanical  principles.  And  in  general  the 
practical  activities  of  mankind  remain  much  the  same  (I 
do  not  say  quite  the  same,  for  there  are  remote  and  indirect 
results  of  the  greatest  importance  in  the  long  run)  whatever 
their  particular  theory  of  the  universe  may  be. 

Now,  let  us  note  the  implication.  We  have  said  a  good 
deal  in  earlier  chapters  about  natural  elimination  and 


484  Animal  Life  and  Intelligence. 

selection.  To  which  category  of  neural  kineses  do  they 
apply — to  those  associated  with  practical  results;  or  to 
those  associated  with  theoretical  results  (supposing  these 
to  obtain  below  the  level  of  man) ;  or  to  both  ?  Clearly  to 
those  associated  with  practical  results.  It  matters  not 
what  theories  a  lion,  or  an  adder,  or  a  spider  hold  (supposing, 
again,  that  they  are  capable  of  theorizing,  which  I  doubt). 
Its  practical  activities  determine  whether  it  survives  or  not. 
So,  too,  with  men,  so  far  as  they  are  subject  to  natural 
elimination.  It  matters  not  what  may  be  the  nature  of 
their  thoughts,  their  aesthetic  yearnings,  their  ideals. 
According  to  their  practical  conduct,  they  are  eliminated  or 
escape  elimination.  In  other  words,  elimination  or  natural 
selection  applies  only  remotely  or  indirectly  to  the  human 
race  regarded  as  theorists,  aesthetes,  or  interpreters  of 
nature. 

Before  proceeding  to  indicate  to  what  laws  our  theories 
and  interpretations  of  nature  and  moral  ideals  are  subject, 
we  may  note  that  there  are  sundry  activities  of  man,  the 
outcome  of  his  conceptual  thought  and  emotion,  which  are 
also,  under  the  conditions  of  social  life,  to  a  large  extent 
beyond  the  pale  of  elimination.  I  refer  to  the  aesthetic 
activities — music,  painting,  sculpture,  and  the  like ;  in  a 
word,  the  activities  associated  with  art,  literature,  and  pure 
science.  These,  in  the  main,  take  rank  alongside  the  ideas 
of  which  they  are  the  outward  expression.  Natural  selec- 
tion, which  deals  with  practical,  life-preserving,  and  life- 
continuing  activities,  has  little  to  say  to  them.  They  are 
neutral  variations  which,  so  far  as  elimination  is  concerned, 
are  neither  advantageous  nor  disadvantageous,  and,  there- 
fore, remain  unmolested.  _ 

We  may,  therefore,  fully  agree  with  Mr.  Wallace,  when 
he  says,*  "We  conclude,  then,  that  the  present  gigantic 
development  of  the  mathematical  faculty  [as  also  of  the 
musical  and  artistic  faculties]  is  wholly  unexplained  by  the 
theory  of  natural  selection,  and  must  be  due  to  some 
altogether  distinct  cause."  Nay,  we  may  go  further,  and 

*  "  Darwinism,"  p.  467. 


Mental  Evolution.  485 

say  that  it  is  only  by  misunderstanding  the  range  of 
natural  selection  as  an  eliminator  that  any  one  could  suppose 
that  these  faculties  could  be  explained  by  that  theory. 

We  must  admit,  then,  that  there  are  certain  neural 
kineses  which,  from  the  fact  that  they  are  unassociated 
with  life -pre  serving  and  life-continuing  activities,  are  not 
subject  to  the  law  of  elimination  ;  and  in  the  development 
of  which  natural  selection  cannot  have  been  an  essential 
factor.  These,  in  their  metakinetie  aspect,  are  conceptual 
thoughts,  emotions,  and  ideas.  Eemembering  the  distinc- 
tion drawn  in  the  chapter  on  "  Organic  Evolution " 
between  origin  and  guidance,  let  us  proceed  to  inquire,  first, 
how  these  ideas  have  been  guided  to  their  present  develop- 
ment ;  and,  secondly,  how  we  may  suppose  these  special 
variations  to  have  originated. 

To  understand  their  development,  we  must  understand 
their  environment.  The  environment  of  metakineses  is,  as 
we  have  already  seen,  constituted  by  other  metakineses. 
What  we  have  now  to  note  is  that  the  environment  of  con- 
ceptual ideas,  as  such,  is  constituted  by  other  ideas.  The  im- 
mediate environment  of  an  hypothesis  is  other  hypotheses  ; 
of  a  moral  ideal,  other  moral  ideals ;  of  an  aesthetic  thought, 
other  aesthetic  thoughts ;  of  a  religious  conception,  other 
religious  conceptions.  But  not  only  are  ideas  environed 
by  ideas  of  their  own  order ;  they  are  environed  by  ideas 
of  other  orders.  Thus  a  scientific  hypothesis  or  a  moral 
ideal  may  be  in  harmony  or  conflict  with  religious  concep- 
tions, and  its  fate  may  be  thereby  determined ;  or  a 
religious  conception  may  be  in  harmony  or  conflict  with 
psychological  principles,  and  its  acceptance  or  rejection 
thereby  determined.  So  that  we  may  say,  in  general,  that 
the  environment  of  an  idea  is  the  system  of  ideas  among  which 
it  is  introduced. 

Of  course,  it  must  be  clearly  understood  that  it  is  with 
the  individual  mind  that  we  are  dealing  The  scientific 
ideas,  moral  ideals,  aesthetic  standards,  religious  concep- 
tions, of  a  tribe,  nation,  or  other  community,  are  simply 
representative,  either  of  the  general  views  of  the  majority 


Animal  Life  and  Intelligence. 


of  the  individuals,  or  more  frequently  of  a  majority  among 
a  cultivated  minority.  In  any  case,  we  have  seen  that 
metakineses  are  and  must  be  an  individual  matter.  For 
each  individual  there  is  a  separate  ideal  world. 

Through  certain  activities,  notably  language  spoken  or 
written,  men  can  symbolize  to  each  other  the  ideas  that  are 
taking  metakinetic  shape  in  their  own  minds.  All-im- 
portant, however,  as  is  this  power  of  intercommunication 
by  means  of  language,  it  does  not  a  whit  alter  the  fact  that 
the  idea  and  its  environment  have  to  work  out  their  rela- 
tions to  each  other  separately  in  each  individual  mind. 
My  neighbour  may  symbolize,  through  language,  his  ideas 
in  such  a  form  that  similar  ideas  may  be  called  up  in  my 
mind ;  but  it  is  there  that  they  have  to  make  good  their 
claim  for  acceptance  in  the  environment  of  the  system  of 
ideas  among  which  they  are  introduced. 

Now,  what  is  the  guiding  principle  of  the  evolution  and 
development  of  ideas  in  the  world  of  their  metakinetic 
environment  ?  Is  there  any  principle  analogous  to  that  of 
elimination  which  we  have  seen  to  be  of  such  high  impor- 
tance in  organic  evolution  ?  I  believe  that  there  is.  An 
idea  is  accepted  or  rejected  according  to  its  congruity  or 
incongruity  with  the  system  of  ideas  among  which  it  is 
introduced.  The  process  has,  perhaps,  closer  analogy  with 
elimination  than  with  selection,  inasmuch  as  it  would 
seem  to  proceed  by  the  rejection  of  the  incongruous,  leaving 
both  the  congruous  and  the  neutral.  An  idea  or  hypothesis 
may  be  accepted,  at  any  rate  provisionally,  so  long  as  it  is 
not  in  contradiction  to  the  theories  and  beliefs  already 
existing  in  the  mind. 

It  may,  however,  be  objected  that  this  view  is  at  variance 
with  the  familiar  observation  that  there  are  many  excellent 
people  who  hold  and  maintain  theories  which  are  exceed- 
ingly incongruous,  which  seem,  indeed,  to  us  mutually 
antagonistic.  Yes,  to  us.  Brought  into  the  environment 
of  our  system  of  ideas,  one  or  other  of  these  antagonistic 
views  would  be  eliminated  through  incongruity.  Not  so, 
however,  with  those  who  hold  both.  Amid  the  environ- 


Mental  Evolution.  487 

ment  of  a  less  logical  and  less  coherent  system  of  ideas, 
both  can  find  admission,  if  not  as  congruous,  still  as 
neutral.  A  sense  of  their  incongruity  is  not  aroused. 

But  there  are  some  people,  it  may  be  said,  who  con- 
sciously hold  views  which  they  admit  to  be  incongruous ; 
who  base  all  their  scientific  reasonings  on  a  continuity  of 
causation,  but  who,  nevertheless,  believe  in  miraculous 
interruptions  of  that  continuity.  In  this  case,  however, 
the  incongruity  is  made  congruous  in  a  higher  synthesis. 
They  belie  themselves  when  they  suppose  that  they  are 
holding  incongruous  views.  Stated  at  length,  what  they 
admit  is  that  miraculous  interventions  are  incongruous, 
not  for  them,  but  for  those  whose  whole  system  of  thought 
is  cast  in  another  mould  than  theirs — for  the  materialist 
and  the  infidel. 

I  cannot  discuss  the  matter  further  here.  This  is  not 
the  place  to  show,  or  attempt  to  show,  how  the  evolution 
of  systems  of  thought  has  caused,  or  is  causing,  certain 
ideas,  such  as  that  of  slavery,  religious  persecution,  the 
moral  and  physical  degradation  of  our  poor,  to  reach  that 
degree  of  incongruity  which  we  signify  as  abhorrent ;  or 
how  that  evolution  has  caused  yet  more  primitive  ideas  to 
seem  positively  repulsive.  Nor  is  it  the  place  to  show,  or 
attempt  to  show,  how  the  advance  of  scientific  knowledge 
has  been  constantly  accompanied  by  the  elimination  of 
incongruous  conceptions.  I  must  content  myself  with  the 
brief  indication  I  have  given  of  the  principle  of  elimination 
through  incongruity  as  applied  to  ideas. 

It  may  be  said  that  such  a  principle  does  not  account 
for  the  origin  of  the  new  congruous  ideas,  but  only  for  the 
getting  rid  of  old  incongruous  ideas.  Quite  true.  But  I 
have  grievously  failed  in  my  exposition  of  natural  selection 
through  elimination  if  I  have  not  made  it  evident  that  this 
objection  (if  that  can  be  called  an  objection  which,  in 
truth,  is  none)  lies  also  at  the  door  of  Darwin's  gene- 
ralization.* 

*  In  both  cases,  the  question  to  which  an  answer  is  suggested  is  not — 
W  hat  variations  will  arise  ?  but— What  variations  will  survive  ? 


Animal  Life  and  Intelligence. 


Now,  from  all  that  has  been  said  in  this  chapter,  it  will 
be  seen  that,  on  the  hypothesis  of  monism,  we  cannot 
regard  organic  and  mental  evolution  as  continuous  the  one 
into  the  other,  but  rather  as  parallel  the  one  with  the 
other — as  the  kinetic  and  metakinetic  manifestations  of 
the  same  process.  Organic  evolution  is  a  matter  of 
structure  and  activity.  If  the  structure  or  the  activity  be 
not  attuned  to  the  environing  conditions,  it  will  be  elimi- 
nated, those  sufficiently  well  attuned  surviving.  Turning 
to  the  metakinetic  aspect,  we  have  seen  that  there  are 
certain  mental  processes  which  are  directly  and  closely 
associated  with  activities.  Their  evolution  will  be  in- 
timately associated  with  organic  evolution.  For  if  these 
processes  lead  to  ill-attuned  activities,  the  organism  will 
be  eliminated ;  and  thus  the  evolution  of  well-attuned 
activities  and  their  corresponding  mental  states  will  proceed 
side  by  side.  We  may,  therefore,  say,  not  incorrectly,  that 
these  lower  phases  of  mental  evolution  are  subject  to  the 
law  of  natural  selection. 

But  when  the  neural  processes  which  intervene  between 
stimulus  and  activity  become  more  complex  and  more 
roundabout ;  when,  instead  of  being  directly  and  closely 
associated  with  life-preserving  activities,  they  are  associated 
indirectly  and  remotely ; — then  they  become,  step  by  step, 
removed  from  their  subjection  to  natural  selection.  And 
when,  in  man,  the  metakineses  associated  with  these  neural 
kineses  assume  the  form  of  hypotheses,  theories,  interpreta- 
tions of  nature,  moral  ideals,  and  religious  conceptions, 
these  are,  except  in  so  far  as  they  lead  to  activities  which 
may  conduce  to  elimination,  no  longer  subject  to  the  law 
of  natural  selection,  unless  we  use  this  term  in  a  somewhat 
metaphorical,  or  at  least  extended,  sense.  They  are  subject, 
as  we  have  seen,  to  a  new  process  of  elimination  through 
incongruity. 

Similarly  with  that  wide  range  of  conduct  in  man  which 
is  the  outcome  of  his  conceptual  life,  and  is  removed  from 
those  merely  life-preserving  activities  which  are  still,  to 
some  extent,  under  the  influence  of  natural  elimination. 


Mental  Evolution.  489 

Conduct  is  here  modified  in  accordance  with  the  conceptual 
system  of  which  it  is  the  outcome  and  outward  expression. 
And  this  higher  conduct  is  subject,  not  to  elimination 
through  natural  selection,  but  to  elimination  through  in- 
congruity. Slavery  would  never  have  been  abolished 
through  natural  selection ;  by  this  means  the  modest 
behaviour  of  a  chaste  woman  could  not  have  been  developed. 
To  natural  selection  neither  the  -Factory  Acts  nor  the 
artistic  products  in  this  year's  Academy  were  due ;  by  this 
process  were  determined  neither  the  conduct  of  John 
Howard  nor  that  of  Florence  Nightingale.  Some  evolu- 
tionists have  done  no  little  injury  to  the  cause  they  have  at 
heart  by  vainly  attempting  to  defend  the  untenable  position 
that  natural  selection  has  been  a  prime  factor  in  the  higher 
phases  of  human  conduct.  I  believe  that  natural  selection 
has  had  little  or  nothing  to  do  with  them  as  such.  They 
are  the  outcome  of  conceptual  ideas,  and  are  subject  to  the 
same  process  of  elimination  through  incongruity. 

So  soon  as,  in  the  course  of  mental  evolution,  the  idea 
of  slavery  became  incongruous,  and  in  certain  minds 
abhorrent  and  repulsive,  steps  were  taken  to  check  the 
conduct  which  was  the  outward  expression  of  this  idea.  So, 
too,  in  other  cases.  The  reformer  must  not,  however,  be  too 
far  in  advance  of  his  generation,  if  his  reform  is  to  be  practi- 
cally carried  out.  When  his  ideas  are  so  "advanced"  as 
to  be  incongruous  with  those  of  all  but  a  very  small  minority 
of  his  contemporaries,  even  they  are  forced  to  confess  that 
the  nation  is  not  yet  ripe  for  the  changes  they  contemplate. 

No  one  will  question  that  artistic  products  are  the 
outcome  of  artistic  ideas.  In  the  slow  and  difficult  progress 
of  a  new  school  of  painting  or  of  music,  we  see  exemplified 
the  rejection  of  the  new  ideas  through  their  incongruity 
with  the  old-fashioned  artistic  systems.  Only  gradually  do 
there  grow  up  new  generations  for  whom  these  new  ideas 
are  not  incongruous.  For  them  the  old-fashioned  systems 
become  incongruous ;  and  if  the  school  becomes  dominant, 
artistic  products  embodving  the  old  ideas  are  eliminated 
through  incongruity. 


49°  Animal  Life  and  Intelligence. 

We  are  not  all  alike.  Our  mental  systems  are  different. 
One  artist  "will  introduce  into  his  canvas  effects  which,  to 
the  eye  of  another,  will  at  once  strike  a  jarring  note  of 
incongruity.  To  some  minds  the  institution  of  slavery 
presents  no  incongruity.  There  are  not  wanting  men  for 
whom  the  degrading  moral  and  physical  conditions  under 
which  many  of  our  poor  are  forced  to  live  and  work  present 
little  or  no  incongruity.  To  the  Eussian,  English  fidelity 
to  the  marriage  vow  is  said  to  be  as  incongruous  as,  to  an 
English  woman,  is  the  harem  of  an  Eastern  potentate. 

In  the  higher  phases  of  human  conduct,  then,  the 
activities  are  subject  to  the  law  of  the  ideas  of  which  they 
are  the  outcome — the  law  of  elimination  through  incongruity. 
I  have  said  that  natural  selection  has  little  or  nothing 
to  do  with  these  higher  phases  of  conduct.  But  has  not 
human  selection  through  preferential  mating?  I  believe 
that  it  has ;  and  I  trust  that  it  will  have  a  still  greater 
influence  in  the  future.  It  is  one  of  the  noblest  privileges 
of  woman,  for  with  her  mainly  lies  the  choice,  that  she 
may  aid  in  raising  humanity  to  a  higher  level.  If  once 
the  idea  of  marrying  for  anything  but  pure  affection  could 
become  utterly  incongruous  to  woman's  mental  nature ; 
and  if  once  the  idea  of  perpetuating  any  form  of  moral, 
intellectual,  or  physical  deformity  could  become  equally  in- 
congruous ;  the  bettering  of  humanity,  through  the  exclusion 
of  the  deformed  in  body  and  mind  from  any  share  in  its 
continuance  must  inevitably  follow.  Here,  again,  ideas 
would  determine  conduct. 

And  what,  we  may  now  proceed  to  ask,  is  the  physio- 
logical or  kinetic  aspect  of  this  metakinetic  process  ?  The 
answer  to  this  question  involves  the  conception  of  what  I 
would  term  "interneural  evolution."  Just  as  the  environ- 
ment of  a  conceptual  idea  is  constituted  by  other  conceptual 
ideas,  so  is  the  environment  of  its  neural  concomitant  con- 
stituted by  the  other  neural  processes  in  the  brain.  Just 
as  no  idea  can  get  itself  accepted  if  it  be  in  incongruity 
with  the  system  of  ideas  among  which  it  is  introduced,  so, 
too,  can  no  neural  process  become  established  if  it  be  not 


Mental  Evolution.  491 

in  harmony  with  the  other  neural  processes  of  the  cerebral 
hemispheres.  The  brain  is  a  microcosm;  its  neural  pro- 
cesses are  interrelated ;  and  the  environment  of  any  neural 
process  is  constituted  by  other  neural  processes. 

A  little  consideration  will  show  that  this  must  be  so  ; 
that  it  is  only  the  physical  or  kinetic  aspect  of  what  is 
freely  admitted  when  the  mental  or  metakinetic  aspect  is 
under  consideration.  If  it  be  admitted  that  states  of  con- 
sciousness are  determined  by  other  states  of  consciousness, 
and  that  states  of  consciousness  are  the  concomitants  of 
certain  neural  processes  in  the  brain,  it  follows  as  a  logical 
necessity  that  brain-neuroses,  however  originating,  are 
determined  in  their  evolution  by  other  brain-neuroses ;  and 
that  there  has  been  a  brain  or  interneural  evolution, 
distinct  from  and  yet  intimately  associated  with  the 
evolution  of  other  bodily  structures  and  activities.  The 
more  closely  and  directly  brain-neuroses  are  associated 
with  immediate  activities,  the  more  closely  implicated  is 
interneural  evolution  in  the  process  of  organic  elimination 
through  natural  selection.  But  when  long  trains  of  neuroses 
take  place  in  only  remote  and  distant  connection  with 
other  bodily  activities,  they  are  removed  from  the  process 
of  elimination  through  natural  selection,  and  interneural 
evolution  is  allowed  to  proceed  comparatively  untrammelled. 

I  have  already  indicated  my  belief  that  abstraction 
(isolation),  analysis,  and  conceptual  ideas  have  been 
rendered  possible  through  language,  and  are  excellences 
unto  which  the  lower  animals  do  not  attain.  Hence  I 
regard  this  comparatively  untrammelled  phase  of  inter- 
neural evolution  as  something  essentially  human,  something 
which  differentiates  man  from  brute.  And  I  would  correlate 
man's  greatly  developed  brain — inexplicable,  I  think,  by 
natural  selection  alone — with  this  later  and  special  phase 
of  interneural  evolution.  Even  in  the  lowest  savage  this 
brain-evolution  has  proceeded  a  long  way.  I  am  not  fitted 
in  this  matter  to  offer  an  opinion  which  would  carry  much 
weight.  But  from  all  that  I  have  read  I  gather  that 
savages  have  in  all  cases  elaborated  a  complex — often  a 


492  Animal  Life  and  Intelligence. 

highly  complex — interpretation  of  nature  and  theory  of 
things.  The  interpretation  may  seem  bizarre  and  incon- 
gruous enough  to  us,  full  of  fetishism  and  strange  super- 
stitions, but  it  is  an  interpretation ;  to  the  savage  it 
presents  no  incongruity ;  to  him  the  incongruity  is  in  the 
oddly  assorted  beliefs  of  the  missionary.  His  system  of 
ideas  is,  in  fact,  one  of  the  many  possible  systems  to 
which  mental  evolution  may  give  rise. 

For  what  we  call  systems  of  thoughts,  interpretations 
of  nature,  theories  of  things,  are  so  many  genera  and 
species  which  have  resulted  from  this  later  phase  of  meta- 
kinetic  evolution.  Our  methods  are  at  present  too  coarse, 
our  powers  too  limited,  to  enable  us  to  determine  these 
species  from  their  kinetic  aspect.  The  brains  of  Kaffir  and 
Boer,  of  ploughboy  and  merchant,  of  materialist  and  idealist, 
are  too  subtly  wrought  to  enable  us  to  trace  the  systems  of 
kineses  which  were  the  concomitants  of  their  scheme  of 
beliefs.  But  we  can  learn  something  of  the  genera  and 
species  from  their  metakinetic  aspect  as  symbolized  through 
language  and  other  bodily  activities.  They  fall  into  certain 
groups,  fetishistic,  spiritualistic,  materialistic,  idealistic, 
monistic,  and  so  on,  and  within  these  groups  there  are  sub- 
divisions. This  is  not  the  place  to  consider  them  or  discuss 
their  characteristics.  What  I  wish  to  note  about  them  is 
that,  diverse  as  they  seem  and  are,  each  is  a  coherent  pro- 
duct of  mental  evolution.  In  each,  all  that  is  incongruous 
to  itself  has  been  or  is  being  eliminated. 

There  are  some  people,  however,  who  are  surprised  at 
the  incongruity  of  interpretations  of  nature  among  each 
other.  Fetishism,  they  say,  has  been  proved  to  be  utterly 
false.  It  constitutes  a  hideous  and  grotesque  delirium. 
How  can  that  which  is  utterly  and  completely  false  to 
nature  have  had  a  natural  evolution  ?  Now,  for  the  elite  of 
the  Aryan  race,  whose  systems  of  ideas  have  been  moulded 
in  accordance  with  the  conceptions  of  modern  science,  no 
doubt  the  fetishism  of  the  poor  savage  seems  sufficiently 
incongruous  and  grotesque.  So,  too,  does  the  system  of 
ideas  of  the  Eight  Kev.  Bishop  of appear  no  doubt, 


Mental  Evolution.  493 

to  the  learned  and  eminent  Professor ,  and  vice  versa. 

And  so,  too,  no  doubt,  does  the  system  of  ideas  of  the  white 
man  (who  introduces  firearms  and  firewater,  and  preaches 
the  gospel  of  forgiveness  and  temperance)  appear  to  the 
poor  savage.  Each  in  his  degree  wonders  how  this  falsity, 
this  incongruity,  can  have  had  a  natural  genesis.  But  in 
each  case  the  falsity  and  the  incongruity  is  not  within  the 
system  itself,  but  between  different  systems. 

Once  more,  I  repeat  that  if  the  individual  nature  of  the 
systems  of  ideas  be  not  adequately  grasped,  the  nature  of 
mental  evolution  will  not  be  apprehended.  States  of  con- 
sciousness can  only  be  determined  by  other  states  of  con- 
sciousness ;  and  states  of  consciousness  are  for  the  indi- 
vidual subject,  and  for  him  alone.  Conceptual  ideas  are 
states  of  consciousness;  and  "falsity  to  nature"  means, 
and  can  only  mean,  incongruity  with  the  environing  states 
of  consciousness  in  the  individual  mind.  For  the  savage 
there  is  no  falsity  to  nature  in  his  fetishism.  The  idea 
presents  no  incongruity  with  his  system  of  ideas  ;  no  more 
incongruity  than  filed  teeth,  flattened  head,  or  pierced  nose 
do  to  his  standard  of  beauty.  It  is  with  our  system  of 
ideas  (i.e.  mine  or  yours)  that  his  fetishism  is  false  and 
incongruous.  The  falsity  or  incongruity,  I  repeat,  is  not 
within  the  system  itself,  but  between  different  systems. 

It  may  still,  however,  be  said — Only  one  interpretation 
of  nature  can  be  true ;  all  others  must  be  false.  And  the 
falsity  is  not  merely  incongruity  with  other  ideas  in  other 
systems  of  thought  or  belief ;  it  is  falsity  to  the  plain  and 
obvious  facts  of  nature. 

We  may  freely  admit  that  only  one  interpretation  of 
nature  can  be  true.  But  who  is  to  determine  which  ?  Who 
can  decide  the  question  between  monist  and  materialist  ? 
Who  dare  arbitrate  between  the  bishop  and  the  professor  ? 
The  criterion  of  fitness  in  this  case,  as  in  others,  is  survival ; 
and  who  can  say  what  existing  interpretation  of  nature  (if 
any)  shall  outlive  all  its  competitors  ?  Who  can  say  what 
will  be  the  nature  of  the  further  evolution  of  any  existing 
philosophical  creed  ?  The  elimination  of  the  false  is  a  slow 


494  Animal  Life  and  Intelligence. 

and  gradual  process ;  and  many  degenerate  systems  of 
ideas  may  linger  on  in  the  darker  corners  of  the  world  of 
men.  False  or  out  of  harmony  as  they  seem  to  be  with 
the  higher  phases  of  development ;  false  or  out  of  harmony 
as  they  would  be  with  a  different  and  more  exalted  environ- 
ment ;  they  are  not  false  or  out  of  harmony  with  the 
environment  in  the  midst  of  which  we  find  them ;  they  are 
not  false  or  out  of  harmony  with  "  the  plain  and  obvious 
facts  of  nature,"  as  these  exist  for  the  ill-developed  or 
savage  mind. 

The  plain  and  obvious  facts  of  nature,  as  interpreted  by 
men  of  science  in  1890,  have  simply  no  existence  for  the 
untutored  or  the  savage  intellect.  For  him  they  have  not 
emerged  into  the  light  of  consciousness.  But  while  we 
cannot  blame  the  savage  for  entertaining  -ideas  which  are 
false  to  facts  which  for  him  have  no  existence,  we  may 
none  the  less  believe  that  his  system  of  ideas  is  not  among 
those  which  are  destined  to  become  predominant  species. 
So  far  as  we  can  judge,  the  winning  species  among  systems 
of  ideas  and  interpretations  of  nature  are  those  in  which 
the  greatest  number  of  ideas  are  fused  into  harmonious 
synthesis ;  in  which  all  the  ideas  are  congruous,  few  or 
none  neutral ;  and  in  which  the  abstract  or  conceptual 
ideas,  when  brought  into  contact  with  concrete  or  perceptual 
states  of  consciousness,  are  found  to  be  in  harmony  and 
congruity  therewith. 

There  is  one  more  question  in  this  connection  on  which 
I  must  say  a  few  words.  How,  it  may  be  asked,  has  the 
world  become  peopled,  for  many  primitive  and  savage  folk, 
with  a  crowd  of  immaterial  spiritual  essences,  so  that  it  is 
scarcely  too  much  to  say  that,  for  some  of  these  peoples, 
everything  has  its  double ;  and  there  is  no  material  exist- 
ence that  has  not  its  spiritual  counterpart  ? 

I  would  connect  this  almost  universal  tendency  with  the 
origin  of  abstract  ideas  (isolates)  through  language.  When 
the  named  predominant  gave  rise  to  the  isolate  (see  p.  374), 
it  could  scarcely  fail  that  the  primitive  speakers  and 
thinkers  should  tend  to  regard  those  qualities  or  properties 


Mental  Evolution.  495 

which  they  could  isolate  in  thought  (conceptually)  as  also 
isolable  in  fact  (perceptually).  And  we  may  well  suppose, 
though  this  is,  of  course,  hypothetical,  that  one  of  the 
earliest  severances  to  be  thus  effected  through  isolation 
was  the  severance  of  mind  and  body.  The  first  phenomena 
that  the  nascent  reason  would  endeavour  to  explain  would 
probably  be  those  of  daily  life  and  almost  hourly  experi- 
ence. Many  familiar  facts  would  seem  to  point  to  the 
temporary  or  permanent  divorce  of  the  part  which  is 
conscious  and  feels,  from  the  part  which  is  tangible  and 
visible.  During  wakeful  life  the  two  are  closely  associated. 
The  visible  part,  or  body,  is  conscious.  But  during  sleep, 
or  under  the  influence  of  a  heavy  blow,  the  visible  part, 
which  before  was  conscious,  is  conscious  no  longer.  The 
conscious  part  is,  therefore,  absent,  but  returns  again  after 
a  while.  On  death  the  conscious  part  returns  no  more. 
The  divorce  of  the  two  has  become  permanent. 

And  then  comes  in  the  confirmatory  testimony  of  dreams. 
In  dreams  the  savage  has  seen  his  enemy,  though  that 
enemy's  body  was  far  away.  Here,  then,  is  the  spirit 
which  has  left  the  body  during  sleep.  In  dreams  also  the 
slain  enemy  or  the  dead  chief  appears.  The  spirit,  per- 
manently divorced  from  the  body,  still  walks  the  earth  in 
spirit-guise. 

Many  occurrences  would  seem  like  the  fulfilled  threats 
of  dead  enemies  or  the  fulfilled  promises  of  dead  ancestors. 
How  can  these  be  explained  ?  Are  they  not  produced  by 
the  ghost  of  the  departed  enemy,  by  the  spirit  of  the 
deceased  ancestor  ?  And  if  these  spirits  are  still  powerful 
to  act,  why  not  petition  them  to  act  in  certain  ways  ? 

Probably  primitive  man  would  explain  all  activities 
anthropomorphically.  What  knows  he  of  gravitation  or 
the  laws  of  the  winds  ?  He  knows  himself  as  agent,  and 
attributes  his  activities  to  the  immaterial  spirit  within 
him ;  for  when  this  is  absent  during  sleep  or  in  death 
these  activities  cease.  All  acting  things  might,  therefore, 
come  to  be  regarded  as  dual  in  their  nature — possessed  of 
a  sensible  material  bodily  part,  and  an  insensible  active 


496  Animal  Life  and  Intelligence. 

spiritual  part.  And  thus  the  whole  world  might  be  peopled 
with  living  existences  of  the  spiritual  order. 

Now,  whether  the  fetishistic  faith  arose  in  some  such 
way  as  this  or  not — and  we  can  never  know  how  it  arose, 
but  can  only  guess — there  would  be  nothing  in  such  primi- 
tive explanations  which  would  violate  the  law  of  congruity. 
They  would  have,  therefore,  a  perfectly  natural  genesis. 
The  attempted  interpolation  at  such  a  stage  of  primitive 
reason  of  any  modern  scientific  conception  would  be  futile. 
It  would  at  once  be  rejected  through  incongruity. 

The  history  of  scientific  conceptions  seems  to  show  that 
they  were  first  adopted  with  regard  to  phenomena  on  the 
very  horizon  of  thought — in  regions,  that  is  to  say,  most 
remote  from  the  central  citadel  of  the  soul.  Only  gradually 
have  they,  little  by  little,  encroached  upon  this  centre  ;  and 
the  application  of  them  to  physiology  and  psychology  is  a 
matter  of  quite  modern  times.  Even  to-day  only  a  minority, 
but  an  increasing  minority,  of  thinkers  are  prepared  in- 
dissolubly  to  unite  the  mind  and  body,  so  long  divorced  in 
thought,  so  completely  united,  as  many  of  us  believe,  in 
their  essential  being. 

I  have  now,  I  trust,  illustrated  at  sufficient  length  the 
principle  of  elimination  through  incongruity  in  interneural 
and  its  associated  metakinetic  or  mental  evolution.  This, 
however,  like  natural  selection,  is  a  matter  of  guidance ; 
we  have  still  to  consider  the  question  of  origin. 

In  truth,  we  know  too  little  on  the  subject  to  enable  us 
to  discuss  it  with  much  profit.  From  the  kinetic  or 
organic  point  of  view,  neural  variations  take  their  place 
among  the  other  variations,  the  origin  of  which,  as  we  have 
already  found,  is  so  hard  to  account  for.  There  may  be  a 
tendency  for  neural  vibrations  to  mutually  influence  each 
other  (like  two  clocks  placed  side  by  side),  and  thus 
gradually  to  drag  each  other  into  one  harmonious  and 
congruous  rhythm.  But  this,  though  not  improbable,  is 
purely  hypothetical.  There  is  the  hypothesis  of  the  in- 
heritance of  acquired  variations,  the  increased  congruity 
acquired  by  the  parent  being  in  some  degree  transmitted 


Mental  Evolution.  497 

to  the  offspring.  There  is  the  view  which  Mr.  Wallace 
adopts  *  with  regard  to  the  origin  of  accessory  plumes,  that 
such  variations  may  be  due  to  "a  surplus  of  strength, 
vitality,  and  growth-power,  which  is  able  to  expend  itself 
in  this  way  without  injury,"  and  not  without  profit.  The 
development  of  the  social  habit,  the  mutual  aid  and  protec- 
tion thus  afforded,  may  well  have  left  a  balance  of  the 
life-energy,  previously  employed  in  individual  self-preserva- 
tion, available  for  this  purpose.  And  then  there  is  always 
the  hypothesis  of  favourable  fortuitous  variations  to  fall 
back  upon. 

On  only  one  of  these  points  do  I  propose  to  say  a  few 
words — that  of  the  possible  inheritance  of  acquired  varia- 
tions. 

Let  us  restate  the  problem  here  for  the  sake  of  clearness. 
There  is,  according  to  the  suggestion  put  forward  in  this 
chapter,  an  interneural  evolution,  leading  to  an  harmonious 
development  of  the  neuroses  in  the  individual  brain.  But 
this  special  evolution  of  the  brain  is  nowise  independent  of 
the  more  general  evolution  of  the  body.  The  human  being, 
as  an  organism,  is  still  subject  to  natural  elimination  and 
human  selection.  Elimination  through  the  action  of  sur- 
rounding physical  conditions,  although  it  has  played  some 
part  in  the  evolution  of  man,  is  not  a  factor  of  the  first 
importance.  Elimination  through  enemies  is  more  im- 
portant, but  has  not  much  bearing  on  the  question  at 
present  before  us — the  evolution  of  the  conceptual.  Elimi- 
nation by  competition,  again,  though  a  factor  of  yet  greater 
importance  in  human  evolution,  has,  nevertheless,  so  far  as 
individuals  are  concerned,  but  little  bearing  on  our  present 
question.  Few  are  eliminated  through  the  absence  of  the 
conceptual  faculty.  Natural  elimination,  then,  is,  as  Mr. 
Wallace  well  pointed  out,  practically  excluded  in  this 
matter.  No  doubt,  in  the  struggle  between  tribes  and 

*  "  Darwinism,"  p.  293.  It  is  strange  that  Mr.  Wallace  did  not  apply  this 
view  to  the  mathematical  and  artistic  faculties  discussed  in  his  last  chapter. 
It  is  true  that  such  application  tends  to  undermine  the  argument  there 
developed.  But  Mr.  Wallace  is  far  too  great  and  conscientious  a  thinker  to 
be  influenced  by  such  a  consideration. 

2K 


498  Animal  Life  and  Intelligence. 

nations,  that  community  is  most  likely  to  be  successful  in 
which  there  is  rational  guidance.  No  doubt,  during  the 
earlier  phases  of  the  development  of  ma-n  on  our  islands, 
the  elimination  of  the  irrational  was  a  factor  in  progress. 
But  if  we  take  the  last  three  centuries  of  English  history,  I 
doubt  whether  it  can  be  shown  that  there  has  been  much 
elimination  determined  by  the  relative  absence  of  conceptual 
ideas  and  emotions. 

Human  selection  has  been  a  much  more  important 
factor.  Those  individuals  which  showed  the  higher  types 
of  intellectual  thought  have  been  constantly  selected. 
Eiches,  rank,  and  social  position  have  been  bestowed  upon 
them.  Of  course,  there  have  been  exceptions ;  great  in- 
tellects have  been  allowed  to  languish  in  their  lifetime, 
and  have  only  obtained  recognition  through  their  works 
after  death.  But  every  day  there  is  less  chance  of  a  genius 
dying  in  a  garret.  And  the  best  intellects,  being  thus 
selected  and  chosen  out  from  among  their  fellow-men,  form 
to  some  extent  a  distinct  social  class.  Segregation  is  thus 
effected ;  and  intermarriage  takes  place  within  this  in- 
tellectual caste,  with  the  result  that  the  conditions  are 
eminently  favourable  for  the  inheritance  of  intellectual 
qualities. 

Now,  is  this  process  of  selection  of  the  intellectual,  this 
segregation  into  a  caste,  and  the  inheritance  of  innate 
intellectual  qualities  sufficient  to  account  for  the  facts  of 
intellectual  progress  ;  or  must  we  call  in  to  our  aid  the 
inheritance  of  individual  increments  ?  I  confess  I  cannot 
say.  Direct  and  satisfactory  evidence,  one  way  or  the 
other,  is  almost  impossible  to  obtain. 

Must  we,  then,  leave  the  question  undecided  ?  I  think 
we  must  so  far  as  direct  evidence  is  concerned.  I  may 
have  a  general  belief  that  there  has  been  some  transmission 
of  acquired  increment  of  intellectual  faculty.  But  unless  I 
can  substantiate  it  by  definite  facts,  I  cannot  expect  to  con- 
vince any  one  who  holds  the  opposite  view.  And  definite 
facts  of  sufficient  cogency  I  am  iinable  to  adduce.  It  is 
practically  impossible  to  exclude  the  influence  of  human 


Mental  Evolution.  499 

selection ;  and  unless  we  can  do  this  the  followers  of  Dr. 
Weismann  will  not  be  satisfied. 

Still,  general  belief — which  means  the  net  result  of  one's 
consideration  of  the  subject — counts  for  something.  We 
must  remember  the  question  is  one  of  origin,  and  not  of 
guidance.  The  guidance  of  human  selection  is  unquestioned 
and  unquestionable.  But  when  we  consider  the  intellectual 
progress  of  the  last  three  centuries,  and  ask  whether  all 
this  has  originated  in  fortuitous  brain-variations,  which 
human  selection  has  simply  picked  out  from  the  total  mass 
of  available  material,  an  affirmative  answer  seems  to  me  a 
little  difficult  of  acceptance.  There  seems  to  have  been 
a  definite  tendency  to  vary  in  this  particular  direction,  a 
general  raising  of  the  intellectual  level,  which  is  difficult  to 
account  for  unless  it  be  due  to  the  persistent  employment 
of  the  intellectual  faculties. 

To  put  the  matter  in  another  way.  I  do  not  think  that, 
during  the  last  three  centuries,  there  has  been  a  large 
amount  of  elimination  of  the  unintellectual.  Such  elimina- 
tion as  there  has  been  of  this  nature  has  probably  been 
more  than  compensated  by  the  slower  rate  of  multiplication 
of  the  intellectual  classes.  Elimination,  then,  in  this 
matter  may  be  practically  disregarded.  But  it  is  obvious 
that  selection,  without  the  removal  or  exclusion  of  the  non- 
selected,  does  nothing  to  alter  the  general  level  *  with  regard 
to  the  particular  quality  or  faculty  concerned.  It  is  merely 
a  classification  of  the  individuals  in  order  of  merit  in  this 
particular  respect.  It  is,  in  a  word,  a  segregation-factor. 
It  arranges  the  individuals  in  classes,  but  it  does  not  alter 
the  position  of  the  mean  around  which  they  vary. 

Let  me  explain  by  means  of  an  analogous  case.  Fifty 
boys,  who  have  been  admitted  to  a  public  school,  await 
examination  in  a  class-room.  They  are  at  present  un- 
classified, but  there  is  a  mean  of  ability  among  the  whole 

*  If  elimination  of  the  unintellectual  (not  necessarily  of  the  unintelligent) 
may  be  excluded,  and  if  the  unintellectual  increase  by  natural  generation 
more  rapidly  than  the  intellectual,  the  general  level  of  intellectuality  must, 
on  Professor  Weismann's  principles,  be  steadily  falling. 


500  Animal  Life  and  Intelligence. 

fifty.  A  week  afterwards  they  are  distributed  in  different 
forms.  Some  are  selected  for  a  higher  form,  others  have 
to  take  a  lower  place.  But  though  selection  has  classified 
the  material,  it  has  not  altered  the  position  of  the  mean  of 
ability  among  the  fifty  boys.  This  can  only  be  done  by 
expelling  a  certain  number  or  excluding  them  from  the 
school. 

Granted,  therefore,  that  elimination  is  practically  ex- 
cluded, human  selection  can  at  most  classify  the  individuals 
according  to  their  intellectual  faculties.  It  cannot  raise  the 
mean  standard  of  intellectuality.  If,  therefore,  this  mean 
standard  has  been  raised  during  the  last  three  centuries, 
there  has  been  a  tendency  to  vary  in  this  particular  direction, 
which  may*  to  say  the  least  of  it,  be  due  to  the  inheritance 
of  individual  increment. 

I  am,  of  course,  aware  that  the  matter  is  complicated 
by  the  increased  and  increasing  diffusion  of  knowledge 
through  the  printing-press  and  by  the  extension  and 
improvement  of  education.  But  education,  to  take  that 
first,  though  it  may  raise  the  level  of  each  generation,  can 
have  no  cumulative  effect.  For  the  effects  of  education 
cannot,  on  Professor  Weismann's  hypothesis,  be  inherited. 
You  may  educate  brain  and  muscle  in  the  individual,  but 
his  heir  will  inherit  no  good  or  ill  effects  therefrom.  Each 
generation  goes  back  and  starts  from  the  old  level.  There 
is  no  summation  of  effect ;  or,  if  there  is,  it  tells  so  far 
against  Professor  Weismann. 

And  with  regard  to  the  diffusion  of  knowledge,  this, 
though  it  brings  more  grist  to  the  intellectual  mill,  can 
have  no  effect  in  raising  the  mean  standard  of  excellence  in 
the  mill  itself.  There  is  more  to  grind  ;  but  this  does  not 
improve  the  grinding  apparatus ;  or,  if  it  does,  it  tells  so 
far  against  Professor  Weismann's  hypothesis.  To  vary  the 
analogy,  the  diffusion  of  knowledge  increases  the  store  of 
available  food ;  but  it  does  not  bring  with  it  any  additional 
power  of  digesting  the  food;  or,  if  it  does,  it  may  be 
through  inherited  increments  of  mean  digestive  power. 

*  It  may  also,  in  part,  be  due  to  "  organic  combination." 


Mental  Evolution.  501 

It  may,  however,  be  maintained  that  there  is  no  con- 
clusive proof  that  the  mean  intellectual  level  of  Englishmen 
to-day  is  any  higher  than  it  was  in  the  days  of  the  Tudors. 
If  so,  of  course,  my  argument  falls  to  the  ground.  I  have 
no  desire  to  dogmatize  on  the  subject.  I  merely  set  down 
the  reasons,  such  as  they  are,  and  for  what  they  are  worth, 
which  lead  me  to  entertain  a  general  belief  that  the 
intellectual  progress*  of  Englishmen  during  the  past  three 
hundred  years  has  been  in  part  due  to  the  inheritance  of 
individually  acquired  faculty. 

Mental  evolution,  then,  is  the  metakinetic  equivalent  of 
interneural,  or,  in  us  vertebrates,  brain-evolution.  The 
brain  forms  a  kinetic  system  in  some  sense  independent  of, 
and  yet  in  constant  touch  with,  the  kinetic  system  of  the 
world  around.  Its  kineses,  though  they  do  not  resemble, 
yet  more  or  less  accurately  represent  or  symbolize,  the 
kineses  of  the  surrounding  universe.  As  the  kineses  of 
the  world  around  are  interdependent  and  harmonious,  so 
are  the  neural  kineses  of  the  brain  interdependent  and 
harmonious.  And  no  modification  of  this  kinesis  which  is 
out  of  harmony  with  the  kinetic  system  already  established 
in  the  brain  can  be  incorporated  with  that  existing  system. 
Such  attempted  modification  is  eliminated  through  in- 
congruity. 

Associated  with  this  brain-kinesis,  and  forming  its 
inner  aspect,  is  a  metakinetic  system  in  which  the  higher 
manifestations  rise  to  the  level  of  full  consciousness  ;  others 
form  sub-conscious  states ;  others  are  unconscious.  But 
the  whole  form  a  coherent  system  answering  to  the  coherent 
kinetic  system. 

Consciousness  is  thus  associated  only  with  the  pheno- 
mena of  that  kinetic  microcosm  which  we  call  the  brain 
(or  other  interneural  system).  Obviously,  therefore, 
it  does  not  and  cannot  deal  directly  with  anything 
outside  the  brain.  Its  knowledge  is  solely  and  entirely 
a  knowledge  of  the  representative  occurrences  of  the 
interneural  system.  But  out  of  these  occurrences  a  sur- 


502  Animal  Life  and  Intelligence. 

rounding  world  of  phenomena  is  constructed  in  mental 
symbolism. 

The  brain  itself,  however,  is  part  of  the  world  of 
phenomena  thus  constructed  in  mental  symbolism  ;  and 
the  world,  therefore,  dissolves  in  pure  idealism,  leaving 
only  a  fleeting  series  of  states  of  consciousness,  if  we  do 
not  assume  the  existence  of  a  system  of  "  things  in  them- 
selves" (noumena),  of  which  kineses  and  metakineses  are 
the  phenomenal  manifestations.  Whether  the  "things  in 
themselves  "  in  any  sense  resemble  their  phenomenal  mani- 
festations, we  cannot  say.  It  is  as  difficult  philosophically 
to  conceive  that  they  can  as  it  is  practically  to  conceive 
that  they  do  not.  And  since,  whether  they  do  or  do  not, 
the  world  we  live  in  is  phenomenal  ;  since  it  is  to 
phenomena  that  we  have  to  adapt  our  conduct ;  since  it  is 
with  phenomena  that  all  our  thoughts  and  emotions  have 
reference ;  since  the  world  we  construct  in  mental  symbolism 
is  the  world  in  which  we  live  and  move  and  have  our 
being ;  it  is  not  only  convenient,  but  logically  justifiable, 
to  call  this  world  of  phenomena  the  really  existing  world 
for  us  human-folk  and  other  sentient  organisms. 

As  in  the  kinetic  interneural  system,  or  brain,  so,  too, 
in  the  metakinetic  system,  no  modification  of  the  meta- 
kinesis  which  is  out  of  harmony  with  the  existing  rneta- 
kinesis  can  be  incorporated  therewith.  Such  attempted 
modification  is  eliminated  through  incongruity. 

In  the  lower  stages  of  mental  evolution,  those  which 
belong  to  the  perceptual  sphere,  where  the  neuroses  are 
closely  connected  with  the  life-preserving  activities  of  the 
organism,  the  survival  or  non-survival  of  the  system  of 
neuroses  is  largely  dependent  on  the  fitness  of  the  asso- 
ciated activities  to  the  conditions  of  life.  But  in  the  highei 
stages  of  mental  evolution,  those  which  belong  to  the  con- 
ceptual sphere,  the  connection  of  certain  brain-neuroses 
with  life -preserving  motor-activities  becomes  less  close  and 
direct.  The  corresponding  ideas,  thoughts,  and  emotions 
become  floated  off  into  a  more  abstract  region.  Here  the 
system  of  ideas,  as  such,  that  is  to  say,  so  far  as  they  ar  e 


Mental  Evolution.  503 

removed  from  life-preserving  activities,  is  determined 
mainly  by  the  law  of  congruity.  But  there  are  several 
such  systems.  There  are,  indeed,  as  many  systems  as 
there  are  minds ;  but  these  may  be  classified  in  several 
distinct  groups,  which  we  may  liken  to  genera  and  species. 
These  are  the  various  interpretations  of  nature,  theories  of 
things,  and  the  like ;  the  systems  of  ideas,  thoughts,  con- 
ceptions, emotions,  beliefs,  which,  as  we  say,  belong  to  us, 
each  and  all,  and  which  determine  to  which  metakinetic 
species  we  belong.  These  are  the  highest  products  of 
mental  evolution  ;  and  among  them  there  is,  so  to  speak, 
a  struggle,  if  not  for  existence,  at  any  rate  for  prevalence. 
Which  shall  eventually  prevail — a  spiritual  interpretation  of 
nature,  a  material  interpretation,  a  monistic  interpretation, 
or  other,  who  shall  say  ?  But,  so  far  as  we  can  judge,  the 
winning  species  among  systems  of  ideas  and  interpreta- 
tions of  nature  are  likely  to  be  those  in  which  the  greatest 
number  of  ideas  are  fused  into  harmonious  synthesis ;  in 
which  all  the  ideas  are  congruous;  and  in  which  the 
abstract  or  conceptual  ideas,  when  brought  into  contact 
with  concrete  or  perceptual  states  of  consciousness,  are 
found  to  be  in  harmony  and  congruity  therewith. 


INDEX. 


Abstract  ideas,  322,  363 

Acceleration,  sense  of,  269 

Acceleration  and  retardation,  221 

Achirus  pellucidus,  83 

Acquired  characters,  are  they 
transmitted  ?  147 ;  habits,  are 
they  inherited  ?  436 ;  variations 
in  the  intellectual  sphere,  497 

Acrcea,  203 

Activities,  organic  basis  of  com- 
parative psychology,  337 ;  of 
animals,  415  ;  voluntary  and 
involuntary,  classification  of, 
462 

Adaptation,  analogous,  117 ; 
modes  of,  119;  special,  ex- 
amples of,  179;  to  varying 
environment,  183 

Advantage  must  be  particular, 
184;  must  be  immediate  and 
not  prospective,  186  ;  must  be 
"available,"  188,211 

Mschna,  2S9 

./Esthetic  preferences  in  insects 
and  birds,  207  ;  aspect  of  sen- 
sation, not  primary,  243 ; 
motive  not  present  to  animal 
consciousness,  409 

ALEXANDER,  Mr.  S.,  "  Moral 
Order  and  Progress,"  463 

ALLEN,  Mr.  Grant,  on  evolution 
of  flowers,  206 ;  on  pleasure 
»nd  pain,  380 

,  Mr.  J.  A.,  on  colour  and 

humidity,  164 

Alternation  of  generations,  46 

Ambli/opsis  spelceus,  271 

American  school  of  evolu- 
tionists, 221 

Amceha,  how  it  feeds,  5 ;  repro- 
duction of,  12,  38  ;  diagram  of, 
12 ;  protoplasmic  functions  of, 
142 
Amphibia,  labyrinthodont,  288 

Anabolism,  constructive  process, 
32 

Analysis  (mental),  321 

Ancon  sheep,  226 

ANDHRSON,  Mr.,  on  one-eared 
rabbits,  226 

Anemone,  sea,  reproduction  of, 
4]  ;  marginal  beads  of,  298  ; 
discrimination  by,  359 

Anger  and  rage,  3»9 

Animal  life,  nature  of,  1;  di- 
versity of,  177 

Animal  intelligence,  differs 
g  nerically  from  man's  reason, 
350 


Animals,  characteristics  of,  1 ; 
divided  into  protozoa  and 
metazoa,  15  ;  and  plants,  their 
relation  to  food-stuffs,  the 
atmosphere,  and  energy,  15  ; 
intelligent  not  rational,  373  ; 
capacities  for  pleasure  and 
pain,  391 

Animistic  ideas  of  savages,  how 
developed,  494 

Anisognathus,  226 

A  nom  ia,  265 

Ant,  sauba,  of  South  America, 
213;  sense  of  taste  in,  253; 
sense  of  smell  in,  258  ;  audi- 
tory organ  of,  267;  intelli- 
gence of,  357  ;  activities  often 
described  as  instinctive,  425 ; 
neuter  insects,  440  ;  Siamese, 
449 

Antagonism,  advantages  of,  394 

Antennae  of  insects,  modifications 
of,  178  ;  of  emperor  moth,  199  ; 
organ  of  hearing  in,  267  ;  modi- 
fied hairs  of,  297 

Antennule  of  crayfish,  259 

Anthophora,  438 

Anticipation,  327 

Antlers  of  deer  in  illustration  of 
growth,  28 

Aphides,  absence  of  fertilization 
in  reproduction,  44 

Appetence  and  aversion,  343,384 

Apus,  46 

Aquatic  organisms,  respiration 
in,  4  ;  sense  of  smell  in,  256 

ARAGO,  M.,  observation  on 
turnspit  dog,  404 

Arctic  hare  and  fox,  84 ;  animals, 
colours  of,  165 ;  fox,  cunning 
of,  366 

ARGYLE,  Duke  of,  on  humming- 
birds, 110 

Artemia  salina  and  milhausenii, 
164 

Artistic  faculties  and  natural 
selection,  484 ;  products,  evo- 
lution of,  489 

Association  a  tendency  to  inte- 
gration, 183;  perceptual  and 
mimicry,  202;  and  recognition 
marks,  203 

Ateles,  210 

Atmosphere,  relations  of  animals 
and  plants  to,  15 

Attacus,  179 

Attention,  342 

Attidice,  208 

Auditory  apparatus  in  man,  262 


Aurelia,  life-cycle  of,  45 
Australian  mammals  and  others 

convergent,  117 
Automatic  action,  415 
Available  advantage,  188,  211 
Aversion    and    appetence,    343, 


Baboon,  experiments  with,  352 

Bacilli  attacked  by  leucocyles, 
439 

Bacillus  violaceus,  80 

BAILEY,  Mr.  E.  H.  S.,  on  taste, 
251 

BALBIANI  on  Chironomus,  137 

Jialistes,  179 

lUuiiF.TT,  Mr.  W.  F.,  on  sensi- 
tive-flame experiment,  298 

Barrier,  geographical,  99;  time, 
in  physiological  isolation,  105 

BARRINGTON,  The  Hon.  Daines, 
on  song  of  linnet,  454 

BATESON,  Mr.  W.,  on  lateral 
line,  252;  on  fishes  hunting 
by  scent,  256 ;  on  smell  in 
shrimps,  etc.,  260  ;  on  hearing 
in  fishes,  264  ;  on  hearing  in 
Anomia,  265 ;  on  sight  in 
fishes,  286;  on  rockling  and 
sole,  352  ;  on  fascination  in 
fishes,  388 

Bats,  tabulated  measurements  of 
wing-bones  of,  65-73;  wings, 
fortuitous  variations  in,  235; 
experiment  with,  247 

Beauty,  standard  of,  206;  sense 
of,  407 

Beaver,  change  of  habit  in,  445 

BECCARI  on  gardener  bower  bird, 
408 

BECKER,  Alexander,  on  varia- 
tions in  the  balance  of  life,  112 

Bees,  divergent  development  of, 
58;  cuckoo,  90;  latency  in, 
228 ;  sense  of  taste,  253 ;  sense 
of  smell,  257 ;  smell-hollows, 
259  ;  eyes  and  eyelets  of,  289 ; 
intelligence  of,  357 ;  colour 
preferences  in,  408;  homing 
faculty  in,  428 ;  neuter  insects, 


of  Madeira,   81;    stag-, 
variability  of  male,  180;  ob- 
servations on  dung-,  368 
Begging  in  dogs,  345 
BEUKKLEY,  Bishop,  quoted,  475 
BEKT,  M.  Paul,  limits  of  sensi- 
bility to  light,  296 


506 


Index. 


BIDIE,  Mr.  George,  anecdote  of 

Cattle,  of  Falkland  Islands,  203 

Construct      and      construction 

cat,  370 

Causation,  327 

(mental),  312  ;  three  stages  of, 

BINET,    M.,    "Psychic   Life   of 

Cell,   diagram    of   animal,    10; 

324  ;  inevitable  nature  of,  332  ; 

Micro-organisms,"  360 

controlled  explosions  in,  31 

in  mammals,  338 

Birds,  influence  of  food-yolk  on 

Cessation  of  selection,  effects  of, 

Continuity  of  reproductive  cells, 

development    of,    56;    diver- 

172 

131;    germ  -plasm,   13«;   cel- 

gence   among,    97  ;    breeding 

Cluztodon,  83 

lular,  142  ;  in  mental  develop- 

area    of     comparatively    re- 

Chcetogaster   limncei,  reproduc- 

ment, 373 

stricted,  101  ;  humming,  Duke 

tion  of,  42 

Convergence,  phenomena  of,  117 

of  Argyle  on,  110;  destruction 

Chaffiuch,  nest  of  New  Zealand, 

Co-ordinants,  303 

of  eggs  of,  189;  game-,  white 

454 

COPE,  Prof.,  on  the  effects  of  use, 

and  black  crossed.  225  ;  taste 

Chamaeleon,  286 

210  ;  and  HYATT,  Prof.,  on  re- 

in, 251;  smell  in,  256;  hearing 

Chance,  236 

tardation  and  acceleration,  221 

in,  264  ;  sight  in,  284  ;  colour- 

Change  of  conditions,  163 

Correlated  variation,  59,  216 

vision  in,  285  ;  gardener  bower, 

Characters,  specific,  110 

CORTI,  organ  of,  263 

408  ;  humming,  nests  of,  408  ; 

CHARBONNIER,  Mr.  Henry,  mea- 

Coryne, Prof.  Weismann  on,  139 

perfect  instincts  of  proecoces, 

surements  of  bats,  63 

COUCH,  Mr.,  on  goldfinch  song, 

424;     love    antics    of    satin 

CHATTOCK,  Mr.  A.  P.,  his  ex- 

454 

bower,    450  ;    nests    of,    453  ; 

periments    on   colour-  vision, 

Crab,  protective  resemblance  in, 

song  of,  454 

280;    letter  to,  on   dog   and 

87  ;     hermit,    195  ;     habit    of 

BLOCHMANN  on  the  development 

picture,  341 

decking  itself,  457 

of  the  drone,  153 

CHESHIRE,  Mr.,  on  smell-hollows 

Crayfish,  smell  in,  259  ;  auditory 

Blood,  circulation  of,  22! 

in  bees,  259 

organ  of,  266 

Body  as  distinguished  from  re- 

Chickens' aversion  to  protected 

Crossing,  effect  on  reversion,  230 

productive  cells,  131 
BOLL  and  KDHITE,  Messrs.,  on 

caterpillars,     352  ;    perfectly  i  Cruelty  in  cat,  objective,  400 
instinctive  activities,  424           1  Crustacea,  eyes  of,  292 

retinal  purple,  276 
BOLTON,  Miss  Caroline,  on  the 

C/iironamus,  reproductive  cells 
of,  137 

Ctenomys,  194 
Cuckoo,  the  nameonomatopoetic, 

bat,  247 

Choice,  458 

322  ;   habits  intelligent,  436  ; 

Bombus   muscorum,    90;    lapi- 

Circulation  of  the  blood,  22 

ejecting  young  birds,  437 

darius,  91 

Classification,  323 

Curiosity  in  prong*horn,  339 

Bombyx  quercus,  258 

CLIFFORD,   W.    K.,  on    human 

Cuttlefish,  eyes  of,  293 

Bower  bird,  408,  450 

consciousness,    341  ;     on    the 

C'yclas,  265 

Brain,  31  ;  decreased,  of  rabbits 

eject,    476  ;    on    "  world^on- 

Cycloptera  speculata,  locust  re- 

and ducks,  171  ;  a  microcosm, 

sciousness,"  479 

sembling  leaf,  86 

491 

Clover  and  bees,  113 

BREHM'S,  Thierleben,  quotation 

Clytus  arietis,  87 

from,  405 

Cockchafer,    smell  -hollows    of, 

DALLiNGER,Dr.,  his  temperatnre- 

Brine  shrimp,  modified  by  sa- 

259 

experiments  on  monads,  147 

linity  of  water,  164 

COCKERELL,  Mr.,  on  variations 

Danais,  203 

BROOKS,  Prof.  W.  K.,  his  modi- 

in  snailg,   75  ;    on  effects    of 

Daplmids,   absence  of  fertiliza- 

fication of   pangencsis,    134  ; 

moisture,  239 

tion   in   reproduction   of,   45  ; 

on  the  greater  variability  of 

Cockroach,   diagram   of  trachea 

colour  -  vision    in,    292,    296; 

the  male,  237 

or  air-tubes  of,   3;    sense  of 

leucocvtes  of,  439 

BROWN,  Prof.  Crum,  on  sense  of 

taste  in,  253  ;  sense  of  smell    DARWIN,  Charles.  Natural  selec- 

acceleration,  270 

in,  258 

tion  and  the  struggle  for  exist- 

BROWNE, Sir   J.    Crichton,   on 

Cocoon,  collective,  429 

ence,  77  ;  divides  the  principle 

ducks,  171 

Colobus,  210 

of  selection  into  three  kinds, 

Budding,   reproduction  by,  42; 

Colour,   protective  resemblance 

78  ;  on  selection  of  flowers  and 

in  relation  to  heredity,  128 

in,  82  ;  warning  of  inedibility, 

fruits  by  insects,  93  ;  on  sexual 

Bull,    "Favourite,"    prepotent, 

82  ;   dependent   on  humidity, 

selection,  94  ;   on  prevention 

227  ;  reversion  in,  229 

164;  direct  action  of  climate 

of  free  crossing  in  breeding, 

BUXYAN,  John,  on  gateways  of 

on,  164  ;  development  of,  202  ; 

99;    on    differential    fertility, 

knowledge,  311 
BUTLER,  Mr.  Samuel,  on  organic 
memory,  62,  475 

blindness,   273,   279;    pheno- 
mena of,  278 
Combination,  organic,  hypothesis 

104;  on  London  rats,  106;  on 
Galapagos    archipelago,   109; 
on  diverse  adaptation,  111  ;  on 

Butterfly,      protective     resem- 

of, 150,  240 

the  influence  of  old  maids  on 

blance  in,  86  ;  mimicry  in,  87 

Communication  in  dogs,  345  ;  in 

clover  crops,  113;  on  the  in- 

bees, 358 

fluence  of  parent  on  offspring, 

Camel,  wounded,  392 

Compensation  of  growth,  155 

122  ;     on    the     co-ordinating 

Canary,  crested,  225  ;  nest  build- 

Competition,         elimination 

power  of  her  organization,  1  25  ; 

ing  of,  453 

through,  89 

hypothesis  of  pangenesis,  131  ; 

Capon,  taking  to  sitting.  228 

Concept,  325,  326 

on  fur  of  arctic  animals,  165  ; 

Capuchin    monkey,    Miss     Ro- 

Conception, 325 

changes  of  structure  attributed 

manes's  observation  on,  367  ; 

Conceptual  conduct  and  evolu- 

to use  and   disease,  171  ;   on 

sympathy  in,  397 

tion,  488 

blindness  of  tuco-tuco,   194  ; 

CARLYLE,  quoted,  331,  335 

Condor,  rate  of  increase  of,  57 

on  the  principle  of  economy, 

Carp  at  Potsdam,  265 

Conduct,     463  ;      influence     of 

194;  on  sexual  selection,  198  ; 

CARTER,  Dr.  Brudenell,  quoted, 

thought  and  aesthetics  on,  483  ; 

on   preferential  mating,   204; 

285 

conceptual,  and  natural  selec^ 

on  evolution  of  flowers,  205  ; 

Caste,  idea  of,  in  dog,  400 

tion,  488 

on  co-ordinated  variations  in 

Cat,  effect  of  African  climate  on, 

Congruity,  principle  of,  486 

the  elk,  213  ;  on  acceleration, 

164  ;  defining  its  percept,  339  ;     Conjugation  in  protozoa,  39  ;  of 

222  ;  on  ancon  sheep,  226  ;  on 

communication,   345  ;    intelli-        ovum  and  sperm-cell,  42 

prepotency,  227  ;  ou  re  version, 

gence    of,    370  ;    and    mouse,    Consciousness,  32  ;  and  consenti- 

229  ;  on  the  effects  of  crossing, 

399  ;  punishing  kitten,  405 

ence,  326,  362  ;  as  a  criterion 

230  ;   on  fortuitous  variation. 

Caterpillars,   protective    resem- 

of instinct,  432 

236  ;  on  the  subordination  of 

blance  in,  82 

Consentience,  326,  362 

the  conditions  to  the  organism, 

Index. 


507 


236  ;  on  the  greater  variability 

Dromia  vulgarin,  457 

Expectation,  327 

of  male,  237  ;  on  attention  in 

Drones  developed    from   unfer- 

Experience dependent    on    me- 

monkeys, 342;  on  brain  of  ant, 

tilized   ova,  45  ;  second  polar 

mory,  SOS 

358  ;  oil  gestures  of  anger  and 

cell  extruded,  153 

Expression  of  the  emotions,  385 

rage,   389  ;    on  pleasures  and 

DUBOIS,  M.,  on  Proteus,  294 

Eye,  structure  of  in  man,  274  ; 

pains    of    animals,    394  ;     on 

Ducks,  '.Sir  J.  Crichton  Browne 

in  mole,  284  ;  pineal,  287  ;  in 

bravery  of  a  monkey,  396  ;  on 

on,  171  ;  Dr.  Rae  on  instinc- 

insects, 288  ;  facetted,  289  ;  in 

Abyssinian  baboons,  405  ;  on 

tive  wildness  of,  435 

Crustacea,   292  ;    in   molluscs, 

sense  of  humour  in  the  dog, 

Duration  of  life,  186 

292  ;  four  types  of,  294 

406  ;   on  neuter  insects,   440  ; 

on  selection  of  oxen,  441  ;   on 

Eagle,  sclerotic  plates  of,  437 

acquisition  of  fear  of  man  by 

Ear,  263 

FABRE,  M.,  on  Sitaris,  439 

birds,   443  ;    on    satin  bower 

Earthworm,    respiration    In,  4, 

Facetted  eye,  289 

bird,  450 

24  ;  regeneration  of  lost  parts, 

Factors  of  phenomena,  laws  of, 

Death,  natural  introduction  of, 

41  ;    sensitive    to    light,   293  ; 

61 

18H,  193 

outward  projection  in,  359 

Falkland  Islands,  cattle  of,  102  ; 

Deceit  in  dogs,  400 
Degeneration,  183 

EATON,  Rev.  A.  E.,  on  insects  of 
Kerguelen  Island,  81 

birds  of,  443 
Fear,  dread  and  terror,  387  ;  in- 

Desert animals,   inoonspicuous- 

Ecitons,  427 

stinct  of,  443 

ness  of,  89 
DESCARTES  on  pineal  gland,  288 

Economy,  principle  of,  194 
Education  of  ants,  428  ;  of  young 

Feelings  of  animals,  8,  378 
Female.   See  Sex-differentiation. 

Desire,  460,  463 

animals,  455 

Female  and  male  insects,  differ- 

Destruction,  indiscriminate,   as 

Egg  and  hen,  problem  of,  130 

ences    between,    179;    vigour 

opposed  to  elimination,  76 
Development  of  organisms  dis- 

Egg-cell and  sperm-cell,  diagram 
of,  13  ;  conditions  which  deter- 

expended on  offspring,  238 
Fertilization,  nature  of,  42  ;  ab- 

tinct from  growth,  6  ;  repro- 

mine production  of,  60 

sent  in  parthenogenetic  forms, 

duction  and,  36  ;  is  differential 

Eggs,  influence  of  food-yolk  on 

44 

growth,  49  ;   of  a  vertebrate, 
diagrammatic  account  of,  51  ; 

mode  of  development  of,  56  ; 
destruction  of  birds,  189 

Fertility,  differential,  Darwinand 
Romanes  on,  104  ;  of  hybrids, 

comparative,  of  some  verte- 

Ego, or  self,  475 

105 

brates,  220 

EIHER,  Prof.,  on   inhabitants  of 

Fetishism,  its  natural  genesis, 

DE  VRIES,  132,  159 

Nile  valley,   165;    on    Helix 

492 

Differentiation  in  protozoa,  40; 

hortensis,    226  ;    on    instinct, 

FISCHER,  Dr.  Emil,  on  smell,  254 

in    metazoa,  41  ;    during    de- 

436 ;   on  differential  dread  in 

Fish,  respiration  in,  24  ;  protec- 

velopment, 49  ;   of  reproduc- 

birds, 444 

tive     resemblance     in,     83  ; 

tive  cells,  143;    and  integra- 

Eject, meaning  of,  476 

amount  of  food-yolk  in  eggs 

tion,  183  ;  of  tissues,  232 

Elaboration,  183 

of,  220  ;  skate  and  turbot  com- 

Difflugia, 360 

Elephant,  rate  of  increase  of,  57  ; 

pared,  220;  sense  of  taste  in, 

Dimorphism  in  larvae,  187 

intelligence  of,  363,  369;  use 

252  ;  sense   of  smell   in,  256  ; 

Discrimination  in  the  sense  of 

of  tools  by,  370  ;   vindictive- 

sense  of  hearing  in,  264  ;  sense 

touch,     245;      hearing,     262; 

ness  in,  401 

of  sight  in,  286  ;  fascination  in, 

sight,   275  ;    its    fundamental 

Elimination,  as  opposed  to  selec- 

388 ;  love-antips  of,  450 

nature,  338  ;  in  sea-anemone, 

tion,  79  ;  its  three  modes,  80  ; 

FISK,  Rev.   G.   H.  R.,  on  sym- 

359 

as  a  factor  in  the  origin  of  in- 

pathy in  cat,  397 

Disease,  elimination  by,  80 

stinct,  447  ;  of  ideas  through 

Fission,  a  process  of  cell-division, 

Display,  207 
Disuse,  panmixia  and,  189  ;  ne- 

incongruity, 486  ;    as  applied 
to  the  intellectual  faculties,  497 

37  ;  in  protozoa,  38  ;  in  meta- 
zoa, 41 

gative   and  not  positive,  196  ; 

Embryology  negatives  pre  forma- 

Flight, instinctive  nature  of,  425 

use  and,  209 

tion,  50 

FLOURENS,  M.,  on    function  of 

Divergence  among    birds,  illus- 
trated    from     Wallace,      97  ; 

Emotions  exemplified,  382;  the 
expression  of,  385  ;  three  orders 

semicircular  canals,  269 
Flowers  and  fruits,  selection  of, 

through  diverse  adaptation,  111 

of,  391  ;  in  vertebrata,  395 

93;    evolved   through    insect 

DIXON,   Mr.  Charles,  effects  of 

Encystment,  38,  49 

agency,  206 

climate  on  the  colours  of  birds, 

Ends  and  means,  371 

Folliculina,  360 

164  ;  on  chaffinch  nests,  454 

Energy,  relations  of  animals  and 

Food-stuffs,  relations  of  animals 

Dog,    effect    of   Indian    climate 

plants  to,  16 

and  plants  to,  15;  nature  of 

on,   164,    167  ;  greyhounds  in 

Ennomos     tiliaria,    caterpillar, 

and  digestion  of,  25 

Mexico,  167  ;   sense  of  smell 

protective  resemblance  of,  85 

Food-yolk,  influence  of,  on  de- 

in, 255,  338  ;  vague  percept  of, 

Environment,  direct  effects  of  on 

velopment,  55  ;   the  result  of 

339  ;  and  the  feelings  of  other 

the  organism,  163  ;  changes  of, 

parental  sacrifice,  67 

animals,   340  ;    and   pictures, 

in  relation   to  the  organism, 

FORBES,  H.  0.,  on  Javan  spiders, 

341  ;    powers  of  communica- 

183 ;  are  effects  of  direct  or 

90 

tion,   344  ;    swimming  rivers, 

indirect?    233;    instances   of 

FOREL,  M.,  on  taste  of  ants,  253  ; 

365  ;  cleverness  of,  367  ;  sym- 

effects of,  238 

on  vision  of  daphnids,  296  ;  on 

pathy  in,  397  ;  idea  of  caste, 

Equus.  118 

happy  family  of  ants,  428 

deceit,  400  ;  endurance  of  pain,    Eristalis  lenav,  87 

Form-characteristics  of  animals, 

402  ;  sense  of  justice  in,  404  ;     Ethics  in  animals,  413 

2 

punishing  pup,  405  ;  sense  of  |  Euplcea,  203 
humour  in,  406  ;  swimming  a    Evolution  of  older  writers,  50  ; 

Fortuitous  variation,  235 
Fosterage  and  protection,   219; 

deferred  instinct  in,  423  ;  turn-  1      and  revolution,  119;  organic. 

result  of  female  self-sacrifice, 

ing  round  to  make  a  couch,  444  |      177:   meaning  of  term,   182; 

238 

Dog-lish,  sense  of  smell  in,  257           mental,  464  ;  organic  and  men- 

FOTHERGILL,  Mr.,  on  dogs  swim- 

Domestication, variations  effected        tal  not  continuous,  488  ;  inter- 

ming  rivers,  364 

by,  171,  215;  crossing  and  re-       neural,  490 

Fowl,  variations  in,  attributed  by 

version,  230                                   Excrement  of  birds,  resemblance 

Darwin  to  use,  171;  crossing 

Doris  tuberculata,  84                    i      of  spider  to,  90 
Dreaming,  341  ;  and  the  animis-  •  Excretion,  an  essential  life-pro- 

of,  227,  230 
K*>x,  cunning  of,  366 

tic  hypothesis,  495                      |      cess,  3,  29 

FRANCIS,  Mr.  H.  A.,  90 

5o8 


Index. 


FRITSCH,  Dr.,  Fig.  of  skull  of 

Melanerptton,  288 
Frog,  development  of,  6 ;  arrest 

of  life  in,  21;  respiration  in, 

24  ;  fishing,  or  angler-fish,  91 ; 

modified  development  of,  214 ; 

effects  of  simple  stimulus  on, 

305 
Fruits  and  flowers,  selection  of, 


GABET,  Messrs.  H0c  and,  on 
Llama  cow,  333 

Galapagos  Archipelago,  species 
and  varieties  in,  99 ;  climate 
of,  109 

Gattus  banfciva,  230 

GALTON,  Mr.  Francis,  on  the 
coloration  of  the  zebra,  84; 
his  modification  of  pangenesis, 
135 ;  numerical  estimate  of  in- 
heritance, 150,  192 ;  his  inves- 
tigations on  twins,  169;  on 
blended  characters,  225;  on 
the  steps  of  evolution,  227 

Ganglia,  31 

Gannet,  rate  of  increase  of,  57 

Gas-engine,  analogy  of,  30 

GACTIER,  Theophile,  his  cat,  264 

GEDDES,  Prof.  Patrick,  and  THOM- 
SON, J.  A.,  on  anabolism  and 
katabolism,  44;  quoted,  50, 
137,  237 

Gemmules,  pangenetic,  131 

Generations,  alternation  of,  46 

Generic  idea,  326 

Geographical  barriers  a  means 
of  segregation,  99 

Geological  changes,  influence  on 
natural  selection,  113 

Germ-plasm,  continuity  of,  138 ; 
convenience  of,  140 

Gills  of  mussel,  4 ;  as  respiratory 
organs,  24 

Giraffe,  co-ordinated  variations 
in,  212 

Glacial  epoch,  effects  of,  113 

Gland,  pineal,  288 

Goldfinch,  song  of,  454 

GOLDSCHNEIDER,  on  tempera- 
ture-sense, 249 

GOCLD,  Dr.,  on  humming-birds' 
nests,  408 

GRABER,  Dr.,  on  colour-sensitive- 
ness of  earthworm,  293 

GRANT,  Mr.  G.  L,  on  New  Zea- 
land sparrows,  445 

Grasshopper,  auditory  organ  of, 

Gregarina,  reproduction  in,  38 

GRENACHER,  Dr.,  experiment  on 
moth's  eye,  290 

Grouse,  white  plumage  in,  due 
to  reversion,  229 

GROVE,  Sir  W.  R.,  on  antago- 
nism, 394 

Growth  of  organisms,  5  ;  illus- 
tration of  a  deer's  antler,  28 ; 
law  of,  after  mutilation,  126 

Guidance  distinguished  from  ori- 
gin, 242 

Guillemot,  eggs  of,  410 

GLLICK,  Rev.  J.  T.,on  landshells 
of  Sandwich  Islands,  109;  on 
tendency  to  divergence,  151 

GI-PPT,  Mr.,  on  crab  of  Solomon 
Islands,  87 


Habits  of  animals,  415 

Habitual  activities,  420;  sense 
of  satisfaction  in  performance 
of,  421 

HAECKEL,  Prof.,  plastidules  of, 
125 ;  theory  of  perigenesis,  159 

Halictus  cylindricus,  90 

HAMERTON,  Mr.  P.  G.,  on  the 
ignorance  of  animals,  333 

HAMILTON,  Sir  Wm.,  quoted,  470 

HANCOCK,  Mr.  John,  on  instinct 
of  cuckoo,  437 

HASSE,  E.,  on  humble-bees,  259 

HAUSER,  on  cockchafer,  259 

HAYCKOFT,  Mr.  J.  B.,  on  taste, 
250 

Hearing,  sense  of,  261 

Heliconia,203 

Helix,  nemoralis  and  hortensis, 
variation  of,  75,  217,  226,  239 

HELMHOLTZ,  Von,  on  colour,  277 ; 
on  local  signs  of  retina,  308 

Hen  and  egg,  problem  of,  130 

HENSEN,  on  shrimps,  266 

HERBERT,  Prof.  T.  M.,  quoted, 
471 

HERDMAN,  Prof.,  on  sea-slug 
(Doris},  84;  his  modification 
of  pangenesis,  135  ;  on  warn- 
ing coloration  in  nudibranchs, 
252 

Heredity,  an  organic  application 
of  the  law  of  persistence,  62 ; 
and  the  origin  of  variations, 
122;  in  protozoa,  123;  and  re- 
generation of  lost  parts,  124; 
failure  of,  192;  and  instinct, 
435 

BERING,  Edward,  on  organic 
memory,  62,  475 

HERON,  Sir  R.,  on  crossing  rab- 
bits, 225 

HEKSCHELL,  Sir  John,  on  colour, 
277 

HERTWIG,  Richard,  observations 
on  Infusoria,  39 

HICKS,  on  Capricorn  beetle,  267 

HICKS'  organ,  267 

HICKSON,  Dr.,  Fig.  of  eye  of  fly, 
290 

Hipparion,  118 

Hippopotamus,  instinctive  acti- 
vities in,  423 

HOLLAND,  Sir  Henry,  on  inheri- 
tance, 223 

Homing  faculty  of  bees.  428 

Horse,  two  different  evolutions 
of,  118 ;  effects  of  use  on  digits 
of,  210 ;  sense  of  pain  in,  392 

HOWSE,  Prof.,  antennule  of  cray- 
fish, 259 

HUBER,  Pierre,  on  smell  in  bees, 
257;  judgment  and  instinct, 
452 

Hue  and  GABET,  Messrs.,  on 
Llama  cow,  333 

HUGGINS,  Dr.,  his  dog  Kepler, 
396 

Humming-birds,  110 

Humour,  sense  of,  in  dog,  406' 

HI-XLEY,  T.  H.,  on  limitation  of 
variations,  151 ;  on  neurosis 
and  psychosis,  465 

HYATT,  Prof.,  on  acceleration  and 
retardation,  221 

Hybrids,  fertility  of,  105 

Hydra,  reproduction  of,  14,  41 ; 
diagram  of,  43;  artificial  divi- 


sion of,  124:  budding  in,  128; 

sexual  reproduction  of,  129 
Hydra  tuba,  and  medusa  of  aure- 

lia,  45 
Hydroids,   development    of,  46; 

Weismann  on,  139 
Hymenoptera,  antennary  struc 

turesof,  297;  instincts  of  social, 

441,  448 

Ichneumon  fly,  instinct  of,  430 
Ichthyosaurus,  pineal  eye  of,  288 
Icterida,  454 
Idea  of  an  object,  313 
Ideas,  conceptual,  their  environ- 
ment, 485 ;  the  law  of  their 
evolution,  486 
Idealism,  474 
Ignorance  of  animals,  333 
Image,  inverted  in  retina,  311 
Imagination,  constructive,  325 
Imitation  as  a  factor  in  habit  or 

instinct,  443,  453 
Immortality  of  protozoa,  12 
Incongruity,  elimination  by,  486 
Increase,  law  of,  58 
Incubation,  instinct  of,  434 
Individuality,  a  tendency  to  dif- 
ferentiation, 183 
Inference,  conscious  and  uncon- 
scious, 328  ;  in  animals,  36  L 
Infertility  of  isolated  forms,  103 
Infusoria,  reproduction  in,  39 
Inheritance,  exclusive,  a  means 
of  isolation,  104 ;  of  variations, 
223 ;  of  acquired  habits,  435  ; 
of  acquiied  increments  of  in- 
tellectual faculty,  497 
Inhibition,  385;  as  a  condition  of 

volition,  459 

Innate  capacity,  422 ;  its  impor- 
tance, 429 

Insects,  tracheal  respiration  of, 
3,  24;  wingless,  of  Madeira, 
81 ;  of  Kerguelen  Island,  81 ; 
mimicry  and  protective  re- 
semblance in,  85,  88 ;  segrega- 
tion by  colour,  101;  antennas 
of,  178  ;  mouth-organs  of,  179 ; 
and  the  evolution  of  flowers, 
206;  sense  of  touch  in,  248; 
taste  in,  253 ;  smell  in,  257  ; 
hearing  in,  266 ;  sight  in,  283 ; 
perceptual  powers  of,  357  ; 
neuter,  440 

Instinct  and  available  advantage, 
211;  consideration  of,  415; 
perfect,  imperfect,  and  incom- 
plete, 422  ;  deferred,  423 ;  blind 
prevision  in,  429 ;  gratification 
in  performance  of,  430 ;  con- 
sciousness and,  432;  primary 
and  secondary,  434  ;  three 
factors  in  the  origin  of,  447  ; 
as  influenced  by  intelligence, 
452;  by  imitation,  453;  by  edu- 
cation, 455 ;  as  distinguished 
from  intelligence,  457 
Instinctive  emotion,  390,  395 
Integration  and  differentiation, 

183 

Intellectual  development,  486 
Intelligence  involved  in  selec- 
tion, 95;  distinguished  from 
reason,  330,  365 ;  lapsed,  435 
involved  in  instinct,  440;  as 
influencing  instinct,  452;  cri- 
teria of.  456 


Index. 


509 


Interbreeding  and  intercrossing, 

Life-area,  expansion    and    con- 

Mathematical faculty  and  natural 

97 

traction  of,  114 

selection,  484 

Interneural  evolution,  490 

Limits  of  vision,  281  ;  of  sensa- 

MADPAS,  M.,   observations   on 

Interpretations  of  nature,  genera 

tion,  299 

infusoria,  39 

and  species  of,  492 

Limnceus  truncatulus,  48 

MATER,  on  mosquito,  267 

Isle  of  Man,  tortoiseshell  butter- 

LINCECUM,   Dr.,    on    habits   of 

McCooK,  Dr.,  sense  of  smell  in 

fly  of,  81 

Texan  ants,  425 

ants,   258;    habits  of   Texan 

Isolates,  322,  364 

Linnet,  song  of,  454 

ants,  425 

Isolation,  organic,  or  segregation, 

Lion,  observation  on,  400 

McCosH,  Dr.,  quoted,  391 

99  ;  mental,  or  abstraction,  322 

Liver-fluke,  life-history  of,  47 

Means  and  ends,  371 

Local  signs,  308 

Medusa,  46  ;  sense  of  hearing  in. 

Localization,  307  ;    in  animals, 

265  ;  eyes  of,  293  ;  localization 

JAEGER,  Dr.,  on  crossing  of  pigs, 

230 

338  ;  in  medusa,  359 
LOCKE,   on   difference   between 

by,  359 
Melanerpeton,  288 

JENKINS,    Mr.    H.   L.,  on    the 
elephant,  363 
Judgment,  330 

man  and  brute,  349 
Logos  makes  man  human,  375 
LONBIERE,  on  instincts  of  Siam- 

MELDOLA, Prof.  R.,  239 
Memory,  the    revival    of   past 
impressions,     304  ;      organic, 

ese  ants,  449 

Butler  and  Hering  on,  62 

LOTZE,  quoted,  379 

Mental  evolution,  464 

Kallima  paralecta,  leaf-butter- 

LUBBOCK,   Sir   J.,  "Senses   of 
Animals,"  246  ;  sense  of  smell 

MERCIER,   Dr.   Charles,   on   the 
criteria  of  intelligence,  456 

fly,  86 
KANT,  quoted,  476 
Katabolism,  a  disruption  or  ex- 

in ants,  258  ;   auditory  organ 
of  ant,  267;  on  Hicks's  organ, 
267  ;    on  colour-sense  in  dog, 

MERRIFIELD,   Mr.,   experiments 
on  moths,  238 
Metabolism,  32 

plosive  process,  32 
Kea,  of  New  Zealand,  446 
Keimplasma.    See  Germ-plasm 
Kentish  plover,  83,  217 
Kepler,  Dr.  Huggins's  dog,  396 
Kerguelen  Island,  wingless  in- 

283; in  insects,  291  ;  in  Daph- 
nia,  292  ;  on  limits  of  colour- 
vision,    296  ;     on    antennary 
structures    in    hymenoptera, 
297  ;  on  power  of  communica- 
tion in  dog,  345;  in  ants,  358  ; 

Metakinesis,  467 
Metamorphosis  and  transforma- 
tion, 7 
Metaphyta,  15 
Metazoa,  15 
Methona,  87 

sects  of,  81 

on  colour  preferences  in  bees, 

MIALL,  Prof.,  Fig.  of  touch-hair 

Kinesis,  467 
Kingfishers,  446 
KIRBT  and  SPENCE,  localization 

407  ;  on  instinct  of  play  and 
sympathy  in  ants,  414;     on 
homing  faculty  in  bees,  428  ; 

of  an  insect,  248 
Mice,  white  and  grey,  crossed, 
225 

of  smell  in  insects,  258;   on 

on  sitaris,  439 

Microbes,  elimination  among,  80 

hearing  in  a  moth,  267  ;   on 

Lucanus  cervits,  180 

Micrococcus  prodigiosus,  81 

instinct  of  ichneumon  fly,  430 
Kittens,  instinctive  antipathy  to 

Ludicrous,    sense   of,    in    dog, 
406 

Microstomum  lineare,  reproduc- 
tion in,  42 

dog,  396 
KLEIN,  Mr.  S.,  on  Bornbyx  quer- 
cus,  258 

LTJMSDEN,  Sir  Harry,  on  part- 
ridges, 398 

Mimicry,  87  ;  as  evidence  of  per- 
ceptual association,  202,  351 

KCHNE,  Messrs.  BOLL  and,  on 
retinal  purple,  276 

of  Darwin,  121 

Mineral    crystals,    analogy    of, 
240 

MITCHELL,  James,  his  delicate 

MACH,  Prof.,  on  Macuta  acustica, 

sense  of  smell,  255 

Labyrinthodont  amphibia,  pineal 

271 

MFVART,    Prof.   St.  George,    on 

eye  in,  288 

Machetes  pugnax,  110,  178 

Saturnia,   163  ;    on    common- 

LAMONT,  on  reindeer,  392 

MACKENNAL,  Mr.  Alexander,  ob- 

sense realism,  316;  on  ideas, 

LANE,  Dr.   Arbuthnot,    on    in- 

servation on  a  cat,  405 

etc.,  326  ;  on  "  practical  intel- 

fluence of   certain  trades  on 

MACLAGAN,  Miss  Nellie,  on  sym- 

ligence," 362;    on  man   and 

structure,  169 

pathetic  action  in  dog,  398 

brute,  374  ;   on  consciousness 

LANGLET,  Prof.,  on  atherial  vi- 

Madeira, wingless  insects  of,  81 

and  oonsentience,  461 

brations,  299 
Language,  322;  the  instrument 

Malei    See  Sex-differentiation 
Male  and  female  insects,  differ- 

Modifiability of  individual  organ- 
ism, 163 

of   analysis,   349  ;    its   origin 

ences  between,    179;    greater 

Modifications    of  antennae    and 

and  effects,  374 
LANKESTER,  Prof.  E.  Ray,  his 

variability  in,  237  ;  vigour  and 
vitality  of,  in  secondary  sexual 

mouth-organs  of  insects,  178 
Mole,  eye  of,  284 

description  of  perigenesis,  159  ; 

characters,  237 

Mollusks,  variety  of,  178  ;  sense 

on  blind  cave-fish,  194 

MALLE,  Dureau  de  la,  on  star- 

of smell  in,  260  ;   hearing  in, 

Lapsing  of  intelligence,  435 

ling,  455 

265;  sight  in,  292 

LARDEN,  W.,  on  the  Rhea,  89  ; 

Mammals,    respiration    in,   21  ; 

Monads,    reproduction    of,    38  ; 

on  instinct  in  a  snakelet,  424 
Larmarckian  school,  209 

early  nutrition  of,  the  result 
of  parental  sacrifice,  57  ;  con- 

temperature experiments  with, 
147 

Larvse,  dimorphism  in,  187 

vergence  in,  117  ;  senseof  smell 

Mongrelization,  168 

Latency,  phenomena  of,  227 
Lateral  line  of  fishes,  252 
Leaf-butterfly,  86 

in,  255;  hearing  in,  263;  sight 
in,  283  ;  perceptions  of,  338 
Man,    elimination    by   physical 

Monistic  hypothesis,  465 
Monkey,  ateles  and  colobus  digits 
of,  210  ;  examining  marsupial 

LEE,  Mr.  Arthur,  on  communi- 

circumstances, 81  ;  alternation 

pouch,  340;  attention  in,  342; 

cation  in  cat,  345 

of  good  and  bad  times,  117; 

capuchin,  intelligence  of,  367 

Leptalis,  87 

reversion  in,  229 

Monospora  biscuspidata,  439 

LEROT,   on    abstract    notion  of 

MANN,    Mrs.,    on    sympathetic 

MOORE,  Mr.  Thomas,  on  hybrids 

danger  in  fox,  348 

action  of  dog,  397  ;  anecdotes 

between  Amherst  and  golden 

Leucocytes,  role  of,  439 

of  dogs,  406 

pheasants,  106 

LEWES,  G.  H.,  437,  462 

Mantis,  protective  and  aggres- 

Mosaic vision,  291 

LETDIG,  on  antennule  of  cray- 

sive resemblance  in,  90 

Mouth-organs  of  infects,  179 

fish,  259 

Marsupials  of  Australia,  117 

Muciparous  canals  of  fishes,  298 

Life,  duration  of,  due  to  natural 

MARTINEAU,  Dr.,  on  wants,  382 

MILLER,  Prof.  Max,  "Science  of 

selection,  186 

Materialism,  464,  471 

Thought,"  325;   on  percepts, 

Index. 


375  ;  on  language  and  thought, 

Oyster-embryo  set  free  early,  56  i  l     phalus    mystaceus,     90;     on 

376  ;    paraphrased,    467  ;    on 

variation  of  Mediterranean,  164 

caterpillars    and     chrysalids, 

materialism,  471 

165;    dimorphism    in    larvae, 

Murex,  292 

187  ;  observations  on  edibility 

JUus  rex  and  imperator,  100 

Pachyrhyncus  orbifex,  87 

of  caterpi  liars,  212;  "  Theories 

Musical  and  artistic  faculty,  484 

Pagurus  prideauxii,  457 

of  Heredity,"  qutotation  from, 

Mussel,  freshwater,  gills  of,  4  ; 

Pain,   massive  and  acute,  379  ; 

214;    on   the    eating    of   un- 

olfactory organ  of,  260 

capacities  of  animals  for,  391 

palatable  insects,  445 

Mutilation,  law  of  growth  after, 

Pangenesis,  182 

Predominant  defined,  349  ;   and 

126  ;  not  the  best  kind  of  evi- 

Panmixia and  disuse,  189 

language,  374 

dence  of  transmitted  modifica- 

Papilionidce, 202 

Preferential  mating,  a  means  of 

tions,  162 

Paradise,  birds  of,  202 

segregation,  102  ;   and  sexual 

Paranucleus  in  protozoa,  39 

selection,  197 

Paramcecium,  reproduction  in,  39 

Preformation  and   evolution  of 

NAEGELI,  159 

Parasites,  how  they  feed,  5 

older  writers,  50 

NAISH,   Mr.  John   G.,  on   the 

Parental  sacrifice  in   birds  and    Prepotency,  227 

cockatoo,  354 

mammals,  57  ;  its  litnita,  186      Presentations  of  sense,  318 

Natural  selection,  variation  and, 

Parrot,  intelligence  of,  353 

Previous  sire,  effect  of,  168 

61  ;    two    modes,  elimination 

Parthenogenetic       forms,       no 

Prevision  as  a  criterion  of  intel- 

and selection  proper,  79  ;  and 

second  polar  cell  in,  153  ;  the 

ligence,  457 

the  effects  of  use  and  disuse, 

drone  an  exception,  153 

Principles,  mechanical,  368 

174  ;  not  to  be  used  as  a  magic 

Parus  palustris,  164 

Process  of  life,  20 

formula,    184;    and   instinct, 
445  ;  and  human  thought,  484 

PEAL,  Mr.  S.,  on  use  of  tools  by 
elephant,  370 

Progress,  or  continuous  adapta- 
tion, 119;  adaptation  to  more 

Nerves,  briefly  described,  246; 

PECKHAM,  Mr.  G.  W.,  on  love* 

complex  circumstances,  183 

afferent  and  efferent,  303 

antics  of  a  spider,  208,  450 

Pronghorn,  curiosity  in,  339 

Nestor  notabilis,  446 

Pecten,  293 

Proposition,  329 

Nests  of  bower-bird  and  hum- 

Pelagic animals,  colours  of,  83 

Protective      resemblance      and 

ming-bird,     408;     instinctive 

PEXZOLDT,  Dr.,  on  smell,  254 

mimicry,  82;   general  resem- 

building of,  453 

Percept,  325,  326 

blance,   83  ;    variable    resem- 

NETTLESHIF, Mr.,  on  a  lion,  400 

Perception,  31  1,324;  in  animals, 

blance,    84;     special    resem- 

Neural processes,  environment 

339 

blance,       86  ;      to      another 

of,  491 

Perceptual  association,  202 

organism,    87  ;     coloration,   a 

Neurosis  and  psychosis,  465 

Perigenesis  of  the  plastidule,  159 

means  of  segregation,  101 

Neuter  insects,  440 

Peripatus,  142 

Protection,  fosterage  and,  219 

New    Zealand     sparrow,    445; 

Persistence,  law  of,  61 

Proteus,  sensitive  to  light,  294 

parrot,  446  ;  chaffinch,  454 

Pheasant,  hybrids  between  Am- 

Protista,  15 

NICHOLS,  on  taste,  251 

herst  and  golden,  106;  golden, 

Protohippus,  118 

Noctule,  66 

hen  with  cock's  plumage,  228 

Protophyta,  15 

NOIKB,  on  concepts,  325 

Phenqodini,  223 

Protoplasm,  10 

Jornada  solidaginis,  90 

Phenomenal    nature  of  object, 

Protozoa,  nature  of,  15  ;    trans- 

NORRIS, Mr.  W.  E.,  quoted,  420 
Noumena,  or  "  things  in  them- 

315, 320,  331 
Photographic    psychology,   320, 

mission  of  acquired  faculty  in, 
147  ;  origin  of  metazoan  varia- 

selves," 470 

326 

tions  in,  156  ;   psychology  of, 

Nucleus  of  animal  cell,  10  ;  as 

Phrynocephalui  mystaceus,  90 

360 

controlling  formative  process 
in,  124 

Physiological  isolation,  104 
Physiological  and  psychological 

Psithyrus  rupestris,  90 
Psychological  and  physiological 

Nutrition  in  illustration  of  the 

activities,  304;  series,  386,417 

activities,  304  ;  series,  386,  417 

process  of  life,  25 

PICTON,  Mrs.  E.,  on  Skye  terrier, 

Psychoses  and  neuroses,  465 

398 

Ptarmigan,  on  colour  of,  165 

Pigeons,  correlated  variations  in. 

Object,  nature  of,  313,  437 

216;   silky  fantail  prepotent, 

Ocelli  in  insects,  288 

227 

Rabbit,  brain  of,  171;   Angora 

Oecodoma  cephalotes,  213 

Pigs,  intestines  of,  171  ;   cross- 

crossed, 225  ;  one-eared,  226  ; 

Onchidium,  293 
Optogram,  276 

ing  of,  226,  230 
Pike,  teeth  of,  437 

deprived  of  long  lip-hairs.  247  ; 
papilla  foliata  of,  250  ;  effects 

Organic  combination,  hypothesis    Pineal  gland,  196,  288 
of,  150,  240  j  Pipistrelle,  wing  of,  64 

Organic  evolution,  177  ;  as  basis  ,  Pipits  as  illustrating  divergence, 
of    comparative    psychology,  I      97 
336  Pitch,  musical,  261 

Organic  growth,  5  j  Plasm,  10 

Organism,  unity  of,  as  regards    Plasmogen,  10 
body  and  germ,  161 ;  relation    Platyglossus,  83 
of,  to  environment.  183  >  Play,  instinct  of,  450 

Organization,  co-ordinating  Pleasure  and  the  special  senses, 
power  of,  125 ;  of  bodily  and  243 ;  massive  and  acute,  379 ; 
mental  activities,  419  capacities  of  animals  for,  391 

Origin,  distinguished  from  guid-    Plecotus  auritt, 


Plesiosaurus,  pineal  eye  of,  288 
PLOSS,  Herr,  on  sex-differentia- 
tion in  man,  59 


ance,  242 

Origin  of  species,  242 
Origin  of  organic  variations,  231  ; 

of  metakinetic  or  mental  varia-    Plover,  Kentish,  83,  217 

tions,  496  I  Polar  cells,  extrusion  of,  51 ;  and 

Ornithoptera.  179  variation.  153 

Otoliths,  265,  271  Postponement  of  action,  385 

OWEN,   Sir    Richard,    suggested    POULTON,  Mr.  E.  B.,  on  colours 

germinal  continuity,  135  |     of  animals,  84 ;  on  Phrynoce- 


of  superabundant  food  on,  394 

RAK,  Dr.,  on  dogs  swimming 
rivers,  364;  on  "abstract 
reasoning  "  in  the  fox,  366 ;  on 
wild  and  tame  ducklings,  435 

Rage  and  anger,  389 

RAMSAY,  Dr.  Wm.,  on  smell,  255 

Rats  of  Solomon  Islands,  100; 
of  the  London  Docks,  106 ;  at 
South  Kensington,  115 

RAYLEIGH,  Lord,  on  colour-blend- 
ing. 283;  on  sensitive-flame 
experiments,  298 ; 

Reality,  meaning  of  term,  314 

Reason  distinguished  from  intel- 
ligence, 330,  365;  as  defined 
by  Mr.  Romanes,  372 

Recepts,  326,  368 

Kecognition-marks,  103;  involve 
perception,  351 

Reconstructs  and  reconstruction 
(mental;,  318 


Index. 


Reflex  action,  415  ;  and  instinct, 

RUSSELL,  Mr.  W.  J.,  on  smell 

SOLLAS,  Dr.  W.  J.,  on  regenera- 

422 

in  the  dog,  255 

tion  of  tentacle  in  snail,  127 

Regeneration  of  lost  parts,  41  ; 

Somatic,  or  body-cells,  193 

in  relation  to  heredity,  124; 

Son  MERINO,  Fig.  of  semicircular 

law  of  growth  concerned  in. 

ftaitis  pulex,  450 

canals,  270 

126 

Salinity  of  water,  effects  of,  on 

SPALANZANI,  his  experiments  on 

Reindeer  wounded,  392  ;  change 
of  habit  in,  445 

brine-shrimp,  161 
Salmon,  new  variety  of,  in  Tas- 

bats, 248 
SPALDING,  Douglas,  on  instinc- 

Remnants or  vestiges,  196 

mania,  99 

tive  emotions,  395  ;  on  perfect 

Reproduction,    nature    of,    13; 

Saturnia,    modification    of,    by 

instincts  of  chicken,  424  ;  on 

and  development,  36  ;  in  the 

changed    food,    163  ;    carpini 

deferred  instinct   in  swallow, 

protozoa,  3s  ;  in  the  metazoa, 
41  ;    by  budding,  42  ;  sexual, 

(emperor  moth),  258 
Savages,  fetishistic  belief  in,  494 

425 
Sparrows  in  New  Zealand,  445 

42  ;  peculiar  modifications  of, 

SCHAUB,  Mr.,  observations  on  a 

Specific    characters,    utility    of, 

45  ;  developmental,  143 

terrier,  405 

110;  constancy  of,  111 

Reproductive    cells,    continuity 

SCHMA.NKEWITSCH   on  Artemia, 

SPENCER,  Mr.  Baldwin.  Fig.  of 

of,  131 

164 

pineal  eye,  288 

Resemblance,     protective,     82  ; 

SCLATER,  Mr.  W.  L.,  on  mimicry 

SPENCER,  Mr.  Herbert,  law  asso- 

aggressive, 90 

in  an  insect,  88 

ciated  with  his  name,  37  ;  phy- 

Respiration   an    essential    life- 

SEDGWICK,   Mr.    Adam,   on  de- 

siological units,  125,  153;  on 

process,  3  ;  in  illustration  of 

velopment  of  peripatus,  142 

lap-dogs,  195  ;  on  the  Irish  elk 

the  process  of  life,  21 
Retardation  and  acceleration,  221 

SEEBOHM,  Mr.  H.,  on  birds'  eggs, 

and  giraffe,  212;  on  diminution 
in  ear-muscles,  215;  definition 

Retina  of  man,  274  ;  of  birds,  284 

Segregation,  99 

of  pleasure  and  pain.  38J  ;  on 

Retinal  purple,  276 

Selection,  as  compared  with  eli- 

aesthetics, 412;  on  instinct  and 

Revenge,  4ul 

mination,  79;  illustrated,  92; 

reflex  action,  422 

Reversion,  191 

artificial,    172;    cessation    of, 

Sperm-cell  and  egg-cell,  13  ;  con- 

Revolution and  evolution,  119 

190;  reversal  of,  193;  sexual, 

ditions  which  determine  pro- 

Rhea, neck  resembling  snake,  88 

or   preferential    mating,    197, 

duction  of,  60 

Rhinolophus       ferri-equinum, 

452  ;  as  a  factor  in  the  origin  of 

Sphex,  instinct  of,  429,  456 

hipposidt-ros,  65 
Rhyme-association  in  parrot,  356 

instinct,  447  ;  as  applied  to  the 
intellectual  faculties.  498 

Spiders,  hunting,  mimicry  in,  89  ; 
Javan,  Mr.  H.  0.  Forbes  on, 

RIBOT,  M.,  on  attention,  343         1  Selenia,    illunaria,    and    illus- 

90;   love-antics   of,  208,  450; 

RICHAHDSON,    Mr.    Charles,   on        traria,  238 

ocelli  of,  289 

railway    servants    killed    by  '  Self,  the,  or  ego,  475 

SPINOZA,  quoted,  61,  379,  460 

train,  388                                       Self-consciousness,  460 

Sponges,  reproduction  of,  41,  42 

RILKY,  Prof.,  on  Phengodini,  223    Semicircular  canals,  262,  269 

SiJongilla,  reproduction  of,  46 

ROMANES,  Prof.  G.  J.,  on  physio-    Senility,  introduction  of,  184 

Spore-formation,  reproduction  by, 

logical  isolation,  104;  on  the 

Sensation  defined,  305,  324 

38 

cessation  of  selection,  190;  on 

Sense-feelings  of  animals,  393 

Squirrel  of  Sarepta,  113 

the  failure  of  heredity,  192; 

Senses  of  animals,  243-;  organic 

Stag-beetles,  variation  in  males 

on  the  reversal  of  selection, 

and  muscular,  244  ;  touch,  245;; 

of,  180 

193  ;  on  sense  of  smell  in  dog, 
on  colour-sense  in  chimpanzee, 
283  ;   on  ideas,   326  ;   on  dog 

temperature-sense,  249  ;  taste, 
250;  smell,  253;  hearing,  261; 
sight,  272  ;  contact  and  telces- 

Star-fish,  embryo  set  free  early,  56 
Starling,  modified  song  of,  455 
ST.  JOHN,  observations  on  a  re- 

cowed by  noise,  340;  on  ab- 

thetic, 249  ;  problematical,  297 

triever,  400 

stract  ideas  in  animals,  348  ; 

Sensibility,   3»5;   variations  of, 

Stenorhynchus,  457 

on  parrot,  353  ;  on  localization 

449        ' 

Sterility,  how  developed,  108 

and  discrimination,  359  ;  ex- 

Sensitive, special  use  of  the  term, 

STEWART,  Mr.  Duncan,  on  sym- 

amples of  animal  intelligence 

9 

pathy  in  cat,  398 

considered,   362;   on  abstract 

Sensitiveness  and  sensibility,  385 

Stimuli,  302 

ideas   in    the  capuchin,   368; 

Sentiments,  391  ;  in  animals,  403 

STRANGE,  Mr.,  on  love-antics  of 

definition  of  reason,  372  ;   on 

Sex-differentiation,  58                    I      satin  bower-bird,  450 

strange  attachments  in  birds, 
396  ;    on    some    emotions    in 

Sexual  union  of  ovum  and  sperm    Striped  ancestor  of  Equidae,  230 
a   source  of   variations,    149;    Struggle  for  existence,  79;  varia- 

animals,  400  ;  on  endurance  of 

characters,     secondary,     197  ; 

tions  in  the  intensity  of,  112 

pain  in  dogs  and  wolves,  402  : 

selection,  197 

STURGE,  Miss   Mildred,  on  the 

on  sense  of   humour    in  dog, 

Shame  in  monkey,  402 

parrot,  355 

4o7  ;  on  indefinite  morality  in 

Sheep,  YOUATT  on,  quoted,  455 

Stylonichia.  observations  of  M. 

animals,    413;    definition    of 

Shells,  land,  of  Sandwich  Islands, 

Maupas  on,  39 

instinct,  422  ;  on  education  of 

99 

SULLY,  Mr.  James,  on  concepts, 

ant,  428  ;   on  homing  faculty 
of  bees,  428  ;  on  consciousness 

SHIPP,  Captain,  experiment  on 
an  elephant,  401 

325  ;  on  propositions,  3^9  ;  on 
judgment  and  reason,  330  ;  on 

and  instinct,   432  ;    summary 

Sight,  sense  of,  272 

emotion,  390  ;  on  sesthetic  sense 

of  his  conclusions  on  instinct. 

Sitaris,  instinct  of,  438 

of  beauty,  411 

434  ;    on  instincts  of  Siamese 

SKKRTCHLEY,   Mr.  S.  B.  J.,   on 

SUTTON,  Mr.  Bland,  on  hen  phea- 

ants, 449;    his   psychological 

leaf-butterfly,  86 

sant  like  the  male,  228  ;  on  the 

scale,  478  ;  on  the  world  as  an 

Slave-making  ants,  425 

action  of  leucocytes,  439 

eject,  479 

Smell,  sense  of,  253 

Swallow  and  swift,  convergence 

Rotation,  sense  of,  269 

Smerinthus  ocellatus,  165 

in,  117  ;  cliff,  of  United  States, 

Rotifers,  absence  of  fertilization 

SMITH,  Mr.  G.  Munro,  on  elimi- 

445 

in  reproduction,  45 

nation  among  microbes,  80 

SWAYNE,  Mr.  S.  H.,  on  the  ele- 

Roux, on  extirpation  of  cleavage- 

Snail,  variations  in  banding  of 

phant,  369 

cell  of  frog's  egg,  214 
EOWBLL,  G.  A.,  on  "  Beneficent 

shells,  75;  sense  of  smell  in, 
260  ;  auditory  sac,  265  ;  eye  of, 

Symbolic  nature  of  mental  pro- 
ducts, 314 

Distribution  of  Pain,"  392 

292  ;  spiculce  amoris  of,  459 

SYMONDS,  Mr.  J.  A.,  on  "  world- 

Ruffs,  variability  of  males,  110, 

Snakes,  mimicry  in,  88 

consciousness,"  478 

178 

Snipe,  drumming  of,  448 

Sympathy  in  animals,  397 

512 


Index. 


Tameness,  instinctive,  435 

area,  113  ;  effect  of  good  times 

Warning-coloration,     82  ;     in- 

TANNER, Miss  Agnes,  on  a  thrush, 

and  hard  times  on,  114  ;  here- 

volves perception,  351 

398 

dity  and  the  origin  of,   122; 

WAHREJT,   Mr.   Robert  Hall,  a 

Tasmanian  salmon,  99 

a  source  of,  in  use  and  disuse, 

dog  anecdote,  344 

Taste,  standard  of,  95,  205  ;  sense 

146  ;  sexual  union,  a  mode  of 

Wasp,  use  of  antennae,  29  1 

of,  25U 

origin  of,  149  ;  in  definite  direc- 

Waste and  repair  essential  life- 

Teeth  of  pike,  437 
Temperature-sense,  249 
Terror,  387 

tions,  151  ;   produced  by  ex- 
trusion of  second  polar  cell, 
153  ;  protozoan  origin  of,  156  ; 

processes,  8 
Water,  changes  of  salinity  in, 
164 

Thaumalia  picta  and  amherstice, 

due  to  the  action  of  environ- 

AV ater-ouzel,  ^46 

106 

ment,  163;   to   the  effects  of 

WATERTON,  Charles,  256 

Thtkla,  instinct  of,  430 

use  and  disuse,  168  ;  to   do- 

WATSON, "  Reasoning  Power  of 

"  Things  in  themselves,"  or  nou- 

mestication,     171;     in    male 

Animals,"  369 

mena,  470 

stag-beetles,  180  ;   in    mating 

WEBB,  Dr.,  his  operation  on  an 

THOMAS,  Mr.  Oldfield,  on  rats  of 
Solomon  Islands,  100 

preferences,  205  ;  co-ordinated 
in  Irish   "elk"  and   giraffe, 

elephant,  369 
WEBER,  on  musical  discrimina- 

THOMSON, Mr.  J.  A.,  Prof.  Patrick 

212  ;  nature  of,  216  ;  in  amount 

tion,  309  ;  on  muscular  sensa- 

GEDDES, and,  on  anabolism  and 

of  developmental  capital,  221  ; 

tion  in  eye,  310 

katabolism,  44  ;  quoted,  50,  137, 

inheritance  of,  223  ;  origin  of, 

WEIR,   Mr.    Jenner,    on    nest- 

237  ;  his  "History  and  Theory 
of  Heredity,"  35 

231  ;  limitations  of,  232  ;  for- 
tuitous, in    bat's  wing,   235; 

building  in  birds,  453 
WEISMANN,  Dr.,  on  continuity 

Thought,  482 

definite  direction  of,  238  ;  in 

of  germ-plasm,  138  ;   on  dis- 

Thrush, hearing  in,  264;  sym- 

limits of  colour-vision,  281  ;  in 

tinctness  of  germ-plasm  fi  om 

pathy  in,  398 

habits  and  instincts,  445,  456  ; 

body-plasm,  140  ;  on  meaning 

TBUNBERG  on  young  hippopo- 

in mental  evolution,  496 

of  second  polar  cell,  1^3  ;  on. 

tamus,  423 

Vertebrata,    diagrammatic    ac- 

protozoan origin  of  variations. 

Tissues  of  the  body,  20 

count  of  development  of,  51 

156  ;   on  the   introduction  of 

TOOKE,  Mr.  Hammond,  on  egg- 

VERWOKN,  Dr.,  on  protozoa,  440 

senility  and  death,  184;    on 

eating  snake,  88 

Vesperlilio  mystacinus,  70 

the  distinction  of  birds'  eggs, 

Tools,  use  of,  by  animals,  370 

Vesperugo  leisleri,  65 

1»9  ;    on  the  effects  of  pan- 

Touch, sense  of,  245 

Vesperugo  noctula.  67 

mixia,    190;  on  acceleration, 

Transformation    and   metamor- 

Vesperugo piputrellus,  69 

222;    his    views    applied    to 

phosis,  7 

Vigour  and  vitality,  application 

instinct,  438  ;  the  intellectual 

Transparency  of   some    marine 

of,  in  male,  237  ;  in  female,  238 

faculties,  497 

organisms,  83 

Vindictiveness,  401 

WESTLAKE,  Miss  Mabel,  on  the 

TREAT,  Mrs.,  her  experiments  on 
caterpillars,  59 

Vision,  272  ;  mosaic,  291 
Volition,  459 

parrot,  353 
Whiskered  bat,  70 

Tricks,  355 

VoluceUa  bombyZans,  90 

White,  in  arctic  forms,  165  ;  Mr. 

Trionyx,  181 

Voluntary  and  involuntary  ac- 

Poulton on  production  of,  202  ; 

Trochui,  292 

tivities,  416 

in  grouse,  instance  of  rever- 

Tuco-tuco, 194 

Vorticella,  38 

sion,  229 

TURNER,    Sir   Wm.,    on    New 

Wildness    of   birds,  instinctive, 

Guinea  natives,  169 

435 

Turkey,  instinctive  emotion  in 

WAELCHLT,  Dr.,  on  colour-glo- 

WILL, F.,  on  taste  in  bees,  253 

the,  395 

bules  in  birds,  284 

WILSON,    Sir    Charles    W.,    on 

Twins,  Mr.   Gallon's  investiga- 

WALLACE, Mr.  A.   R,   tabula- 

wounded camels,  392 

tions  on.  169 

tions    of   variations,    63;    on 

WILSON,  Kdward,  measurements 

TTLOR,  Alfred,  on  coloration  in 

tortoiseshell  butterfly  of  Isle 

of  bats,  63 

animals  and  plants,  201 

of   Man,    81  ;     on    protective 

Wing-bones  of   bats,  measure- 

colours in  fishes,  83  ;  on  diver- 

ment   of,    in    illustration   of 

gence    among    birds,   97  ;  on 

variation,  63 

Udders,  enlarged,  of  cows,  215 
Ultra-violet  rays,  296 

recognition-marks,    1  02  ;    on 
papilionidas  of  Celebes  ;  165  ; 

Words,  "  understanding"  of,  by 
animals,  347 

Unicellular  organism.     See  Pro- 

on   the    dull  colours  of  hen 

Wrasse,  keeness  of  vision  of,  287 

tozoa 

birds,    199;     on      origin      of 

Unity  of  organism,  161,  234 

secondary  sexual    characters, 

Xiphocera,  179 

Use  and  disuse,  146,  209 

200  ;   and  A.  Tylor  on  physio- 

Utility  of  specific  characters,  110 

logical;gnidance,  201  ;  on  pre- 

ferential    mating,     203;     on 

YotJATT  "  On  Sheep,"  455 

reversion  in   grouse,  229  ;  on 

YOUNG,    Thomas,    his    colour- 

Vanetsa  urticce,  165 

migration  in  birds,  428  ;   on 

vision  theory,  277 

Varanus  benegalensis,  288 

nest-building   in    birds,  453; 

YUNG,  his  experiments  on  tad- 

Variation, correlated,    59  ;    and 

on  the  song  of  birds,  455  ;  on 

poles,  59 

natural    selection,    61  ;    tabu- 

materialism, 464  ;  on  mathe- 

lated by  A.  R.  Wallace,  63  ;  in 

matical  and  artistic  faculties, 

wing-  bones  of  bats,  63  ;  advan- 

484, 497 

Zebra,  inconspicuousness  of,  in 

tageous,  neutral,  and  disadvan- 

WALKER, R.,   on  reversion   in 

dusk,  84 

tageous,  95;  in  climatal  and 

bull,  229 

Zuyder    Zee,    new    variety    of 

geographical  conditions,  112  ; 

WARD,  Mr.  J.  Clifton,  on  dog, 

herrings  in,  99 

secular,  in   climate   and  life 

345 

LONDON  :    PRINTED  BT   WILLIAM  CLOWES   AND  SONS,    LIMITED, 
STAMFORD   STREET   AND  CHARING  CROSS. 


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